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Biomedical subjects

M Bonnet

Publications and source records attributed to M Bonnet.

At least 37 records · Page 2Linked to original sources
PubMed2000

Is the 'error negativity' specific to errors?

When subjects make an erroneous response in a choice reaction time task, an error negativity, or error-related negativity (N(E)/ERN), peaking at about 100 ms after EMG onset, has been described. This wave is often considered to be absent on correct response trials. We report a small N(E)/ERN wave on correct response trials during a choice reaction time task in which surface Laplacians were estimated by the source derivation method. This wave is well focused at FCz, and its time course is the same for correct responses trials, incorrect sub-threshold EMG activation trials, and error trials. Current source density maps, also indicate a focus at FCz. A second experiment showed the existence of a N(E) at FCz on correct trials during a simple RT task. Rather than an error detection process per se, we propose that the N(E)/ERN reflects either a comparison process leading secondarily to error detection, or an emotional reaction.

Adult↗
PubMed2000

High-speed memory scanning: a behavioral argument for a serial oscillatory model.

In order to account for the memory span [G.A. Miller, The magical number seven, plus minus two: some limits on our capacity for processing information, Psychol. Rev. 63 (1956) 81-97.], the magical number seven, plus minus two, and high-speed scanning in human memory ¿S. Sternberg, High speed scanning in human memory, Science 153 (1966) 652-654., Lisman and collaborators [O. Jensen, J.E. Lisman, An oscillatory short-term memory buffer model can account for data on the Sternberg task, J. Neurosci. 18 (1998) 10688-10699; J.E. Lisman, M.A.P. Idiart, Storage of 7+/-2 short-term memories in oscillatory subcycles, Science 267 (1995), 1512-1515.] proposed an oscillatory short-term memory buffer model. In this neurophysiological model: "a single brain network can separately maintain up to seven memories by a multiplexing mechanism that uses theta and gamma brain oscillations for clocking. A memory is represented by groups of neurons that fire in the same gamma cycle" ¿O. Jensen, J.E. Lisman, An oscillatory short-term memory buffer model can account for data on the Sternberg task, J. Neurosci. 18 (1998) 10688-10699, p. 10688. To test this model, we tried to modify the memory scanning time by shifting the gamma oscillation frequency. To this aim, we replicated the visual short-term memory scanning task ¿S. Sternberg, High speed scanning in human memory, Science 153 (1966) 652-654., and we simultaneously used the protocol that Treisman ¿M. Treisman, A. Faulkner, P.L.N. Naish, D. Brogan, The internal clock: evidence for a temporal oscillator underlying time perception with some estimates of its characteristics frequency, Perception 19 (1990) 705-743. designed to drive, slowing down or speeding up, a temporal oscillator acting in the gamma range ¿J.G.R. Jefferys, R.D. Traub, M.A. Whittington, Neuronal networks for induced "40 Hz rhythms, Trends Neurosci. 19 (1996) 202-208; W. MacKay, Synchronized neuronal oscillations and their role in motor processes, Trends Cog. Sci. 1 (1997) 176-183; M. Treisman, N. Cook, P.L.N. Naish, J.K. MacCrone, The internal clock: electroencephalographic evidence for oscillatory processes underlying time perception, Q. J. Exp. Psychol. 47A (1994) 241-289.. In this protocol, an auditory periodic stimulus (click train) was delivered at various frequencies during the task. The reaction time (RT), the slope, and the intercept of the linear function associating RT to memorized list length showed systematic modulations according to the stimulation frequency. The predicted driving effects due to the click trains were obtained, consisting of localised modulations of performance on the stimulation frequency band. We argue that memory scanning is indeed paced by a temporal oscillator, thus providing behavioral arguments for the serial oscillatory model of Lisman.

Adult↗
PubMed2000

Adipose tissue metabolism and its role in adaptations to undernutrition in ruminants.

Changes in the amount and metabolism of adipose tissue (AT) occur in underfed ruminants, and are amplified during lactation, or in fat animals. The fat depot of the tail of some ovine breeds seems to play a particular role in adaptation to undernutrition; this role could be linked to its smaller adipocytes and high sensitivity to the lipolytic effect of catecholamines. Glucocorticoids and growth hormone probably interact to induce teleophoretic changes in the AT responses to adenosine and catecholamines during lactation. Fat mobilization in dry ewes is related both to body fatness and to energy balance. The in vivo beta-adrenergic lipolytic potential is primarily related to energy balance, whereas basal postprandial plasma non-esterified fatty acids (NEFA) are related to body fatness, and preprandial plasma NEFA is the best predictor of the actual body lipid loss. Several mechanisms seem to be aimed at avoiding excessive fat mobilization and/or insuring a return to the body fatness homeostatic set point. As well as providing the underfed animal with fatty acids as oxidative fuels, AT acts as an endocrine gland. The yield of leptin by ruminant AT is positively related to body fatness, decreased by underfeeding, beta-adrenergic stimulation and short day length, and increased by insulin and glucocorticoids. This finding suggests that the leptin chronic (or acute) decrease in lean (or underfed respectively) ruminants is, as in rodents, a signal for endocrine, metabolic and behavioural adaptations aimed at restoring homeostasis.

Adaptation, Physiological↗
PubMed2000

Lipoprotein lipase activity and mRNA are up-regulated by refeeding in adipose tissue and cardiac muscle of sheep.

Previous studies in rodents have shown that the lipoprotein lipase (LPL) regulation is complex and often opposite in adipose tissue (AT) and muscle in response to the same nutritional treatment. However, neither LPL responses nor the molecular mechanisms involved in the nutritional regulation have been studied in both AT and muscle of ruminant species. To explore this, we measured the LPL activity and mRNA levels in perirenal AT and cardiac muscle (CM) of control, 7-d-underfed or 14-d-refed ewes. Underfeeding decreased (P < 0.01) LPL activity both in AT (-59%) and CM (-31%), and these activities were restored (P < 0.01) by refeeding (AT, +248%; CM, +34%). Variations of LPL mRNA level measured by real-time reverse transcription-polymerase chain reaction or by Northern blot followed variations of LPL activity: underfeeding decreased AT- and CM-LPL mRNA levels (-58 and -53%, respectively), and refeeding restored (P < 0.01) them in CM (+117%) and increased them over the baseline in AT (+640%). Quantification of either 3.4- or 3.8-kb LPL mRNA levels revealed a predominant (P < 0.001) expression of the 3.4-kb mRNA in AT (60%) and of the 3.8-kb mRNA in CM (56%), without any preferential regulation of one of these mRNA species by the nutritional status. This work reveals a tissue-specific expression pattern of the ovine LPL gene and a pretranslational nutritional regulation of its expression, which is achieved in the same direction in perirenal AT and CM. The different regulation of CM-LPL between ewes and rats probably arises from peculiarities of ruminant species for nutrient digestion and absorption and liver lipogenesis.

3' Untranslated Regions↗
PubMed2000

Changes in spinal excitability during choice reaction time: the H reflex as a probe of information transmission.

The aim of the present study was to investigate the modulations in amplitude of H reflexes elicited in a hand muscle, the flexor pollicis brevis, during the performance of a choice reaction time (RT) task in which this muscle was directly involved. Ten subjects were to choose between a left- or a right-thumb key-press according to the lateral location of a flash of light. The stimulus-response mapping was either compatible or incompatible. Hoffman reflexes were elicited at different times during the RT by stimulation of the median nerve. Twenty-five milliseconds before the voluntary response, the amplitude of the H reflex suddenly increased when the muscle was involved in the response and decreased symmetrically when the muscle was not involved in the response. Mapping compatibility exerted no detectable influence on the changes in spinal excitability. The latter result supports the assumptions that are at the core of Sternberg's additive factor method.

Adult↗
PubMed2000

Effects of zinc and influence of Acremonium lolii on growth parameters, chlorophyll a fluorescence and antioxidant enzyme activities of ryegrass (Lolium perenne L. cv Apollo).

The effects of zinc on growth, mineral content, chlorophyll a fluorescence, and detoxifying enzyme activity (ascorbate peroxidase (APX), EC 1.11.1.11; superoxide dismutase (SOD), EC 1.15.1.1) of ryegrass infected or not by Acremonium lolii, and treated with nutrient solution containing 0-50 mM ZnSO(4) were studied. The introduction of zinc induces stress with a decrease in growth at 1, 5 and 10 mM ZnSO(4) and a cessation of growth at 50 mM ZnSO(4), in ryegrass plants infected by A. lolii or not. This decrease in growth may be due to an accumulation of zinc in leaves. Nevertheless, symbiotic plants showed higher values in tiller number, an advantage conferred by the fungus. After 24 d of Zn exposure, leaf fresh weights and leaf water content were lower in plants growing with Zn in the culture medium and no advantage was conferred by the fungus to its host. An increase in Zn supply resulted in a decrease of the Ca, K, Mg, and Cu content of the leaves, a reduction in the quantum yield of electron flow throughout photosystem II (DeltaF/F(1)(m))and a lowering of the efficiency of photosynthetic energy conversion (F(v)/F(m)), compared to control plants. To counter this zinc stress, detoxifying enzymes APX and SOD increased (100%) when Zn reached the value of 50 mM in the nutrient solution. At 10 mM ZnSO(4), the presence of the fungus in the plant led to an increase in the threshold toxicity of plants to zinc by a diminution of APX activity.

Acremonium↗
PubMed1999

Detection of Epstein-Barr virus in invasive breast cancers.

BACKGROUND: Epstein-Barr virus (EBV) may be a cofactor in the development of different malignancies, including several types of carcinomas. In this study, we investigated the presence of EBV in human breast cancers. METHODS: We used tissues from 100 consecutive primary invasive breast carcinomas, as well as 30 healthy tissues adjacent to a subset of the tumors. DNA was amplified by use of the polymerase chain reaction (PCR), with the primers covering three different regions of the EBV genome. Southern blot analysis was performed by use of a labeled EBV BamHI W restriction fragment as the probe. Infected cells were identified by means of immunohistochemical staining, using monoclonal antibodies directed against the EBV nuclear protein EBNA-1. RESULTS: We were able to detect the EBV genome by PCR in 51% of the tumors, whereas, in 90% of the cases studied, the virus was not detected in healthy tissue adjacent to the tumor (P<.001). The presence of the EBV genome in breast tumors was confirmed by Southern blot analysis. The observed EBNA-1 expression was restricted to a fraction (5%-30%) of tumor epithelial cells. Moreover, no immunohistochemical staining was observed in tumors that were negative for EBV by PCR. EBV was detected more frequently in breast tumors that were hormone-receptor negative (P =.01) and those of high histologic grade (P =.03). EBV detection in primary tumors varied by nodal status (P =.01), largely because of the difference between subjects with more than three lymph nodes versus less than or equal to three lymph nodes involved (72% versus 44%). CONCLUSIONS: Our results demonstrated the presence of the EBV genome in a large subset of breast cancers. The virus was restricted to tumor cells and was more frequently associated with the most aggressive tumors. EBV may be a cofactor in the development of some breast cancers.

Adult↗
PubMed1999

Seroepidemiological and molecular studies of human T cell lymphotropic virus type II, subtype b, in isolated groups of Mataco and Toba Indians of northern Argentina.

We studied plasma samples from 2082 Mataco Indians living in 22 different communities in the western part of Formosa Province, northern Argentina. Samples were screened for HTLV-I/II antibodies by particle agglutination assay. All positive or borderline samples were then tested by an immunofluorescence assay (IFA) on C19 HTLV-II-producing cells. Western blot was used for confirmation of all IFA-positive plasma samples. The crude HTLV-II seroprevalence was 3.0% (62 of 2051), and 0.9% (5 of 588) in children less than 10 years old. The latter result suggests ongoing mother-to-child transmission, probably by breast feeding. There was a marked increase in HTLV-II seroprevalence with age (0.9%, 0-10 years; 1.6%, 11-20 years; 4.4%, 21-30 years; 3.4%, 31-40 years; 7.2%, 41-50 years; 5.7%, >50 years) in both male (p = 0.002) and female subjects (p = 0.00002). None of the 80 non-Indian inhabitants tested was HTLV-I/II seropositive. In a second study, among 105 Toba Indians from a village (Primavera) of the eastern part of this region, 23 were HTLV-II seropositive with a seroprevalence of 59% in those more than 40 years old. From seven of the Indians from Primavera, three others from neighboring regions (including two Tobas and one Pilaga), and one intravenous drug user (IVDU) from Rosario, DNA was extracted from peripheral blood mononuclear cells, and the gp21 transmembrane-encoding gene (590 bp) was amplified by PCR, cloned, and sequenced. LTR sequences were also obtained from the Pilaga, the IVDU, and one Toba. Molecular and phylogenetic analyses revealed that the Indians were all infected with closely related HTLV-II molecular strains belonging to the b subtype, while the IVDU was infected with an HTLV-II subtype a variant. Such data help to make a phylogenetic atlas of HTLV-II among Amerindian tribes and are crucial to gain new insights into the origin and modes of dissemination of this human retrovirus in the Americas.

Adolescent↗
PubMed1999

T2* and proton density measurement of normal human lung parenchyma using submillisecond echo time gradient echo magnetic resonance imaging.

OBJECTIVE: To obtain T2* and proton density measurements of normal human lung parenchyma in vivo using submillisecond echo time (TE) gradient echo (GRE) magnetic resonance (MR) imaging. MATERIALS AND METHODS: Six normal volunteers were scanned using a 1.5-T system equipped with a prototype enhanced gradient (GE Signa, Waukausha, WI). Images were obtained during breath-holding with acquisition times of 7-16 s. Multiple TEs ranging from 0.7 to 2.5 ms were tested. Linear regression was performed on the logarithmic plots of signal intensity versus TE, yielding measurements of T2* and proton density relative to chest wall muscle. Measurements in supine and prone position were compared, and effects of the level of lung inflation on lung signal were also evaluated. RESULTS: The signal from the lung parenchyma diminished exponentially with prolongation of TE. The measured T2* in six normal volunteers ranged from 0.89 to 2.18 ms (1.43 +/- 0.41 ms, mean +/- S.D.). The measured relative proton density values ranged between 0.21 and 0.45 (0.29 +/- 0.08, mean +/- S.D.). Calculated T2* values of 1.46 +/- 0.50, 1.01 +/- 0.29 and 1.52 +/- 0.18 ms, and calculated relative proton densities of 0.20 +/- 0.03, 0.32 +/- 0.13 and 0.35 +/- 0.10 were obtained from the anterior, middle and posterior portions of the supine right lung, respectively. The anterior-posterior proton density gradient was reversed in the prone position. There was a pronounced increase in signal from lung parenchyma at maximum expiration compared with maximum inspiration. The ultrashort TE GRE technique yielded images demonstrating signal from lung parenchyma with minimal motion-induced noise. CONCLUSION: Quantitative in vivo measurements of lung T2* and relative proton density in conjunction with high-signal parenchymal images can be obtained using a set of very rapid breath-hold images with a recently developed ultrashort TE GRE sequence.

Artifacts↗
PubMed1999

Effect of the irrelevant location of the response signal on choice reaction time: an electromyographic study in humans.

Choice reaction time (RT) is shorter when the stimulus corresponds spatially to the response than when the stimulus does not, even when the stimulus location is irrelevant to the task. We used electromyographic measures to document that this effect is the result of a response conflict. The activity of the prime movers of two alternative responses was recorded during the performance of a visual RT task in which the irrelevant spatial correspondence between the stimuli and the responses was varied. Only the premotor component of RT was affected by the stimulus-response correspondence. Correct trials were distinguished according to whether or not the activation of the prime mover involved in the required response was preceded by an activation of the prime mover involved in the alternative response. Double muscular activation trials were more numerous for noncorresponding than for corresponding stimulus-response associations. Furthermore, these trials yielded longer RTs than the single muscular activation trials.

Adult↗
PubMed1998

Amino-acid change in the Epstein-Barr-virus ZEBRA protein in undifferentiated nasopharyngeal carcinomas from Europe and North Africa.

Different Epstein-Barr-virus(EBV) variants were found to be associated with nasopharyngeal carcinoma (NPC). The type-C variant lacks the BamHI site between the BamHI W1* and I* regions and the type-f variant has an extra BamHI site in the BamHI F fragment. The BNLF1 gene (which encodes the LMP1 protein) from a nude-mouse-passaged CAO strain and from NPC biopsies from Taiwanese patients also exhibits variations resulting in structural and functional differences in the protein. The BZLF1 gene encodes the ZEBRA protein which triggers the EBV lytic cycle. A difference has been observed in 8 amino acids in the ZEBRA sequence in B95-8 (Z95) and P3HR1 (ZP3) cell lines. EBV found in NPC biopsies and peripheral-blood cells from Asians was predominantly of the ZP3 type (72%), while 81% of samples from different EBV-associated diseases and peripheral-blood cells from North Africa or Europe were of the Z95 type. We found that an alanine 206 had been replaced by a serine in the Z95 sequence in 72% of the NPC biopsies from European and North African patients. The Zser206 variant is found in a significantly lower percentage (p < 0.001) of other EBV-positive tissues from individuals in the same region (10-33%). In contrast, a 30-bp deletion is observed near the 3' end of the LMP1 gene in the majority of EBV (86%) from NPC and peripheral-blood cells from Asians, whereas a significantly lower percentage (p < 0.001) of NPC biopsies from European and North African patients (56%) have this deletion, as do lymphocytes from control individuals from the same region (36 and 55% respectively).

Africa, Northern↗
PubMed1998

[Postoperative proliferative vitreoretinopathy in rhegmatogenous retinal detachment associated with stage B preoperative proliferative vitreoretinopathy: comparative results of trans-scleral retinopexy with diode laser or trans-pupillary retinopexy with argon laser].

PURPOSE: To compare the rate of severe postoperative PVR in primary rhegmatogenous retinal detachments (RD) associated with preoperative grade B PVR and managed either with transpupillary Argon laser photocoagulation or transscleral Diode laser photocoagulation. MATERIAL AND METHODS: We evaluated 72 primary rhegmatogenous retinal detachment associated with preoperative grade B PVR (retinal tears with curled posterior edges), referred before any failed attempt to reattach the retina. Eleven RD were due to giant tear. The retinopexy was performed using transpupillary Argon laser. photocoagulation in 46 eyes, and transscleral Diode laser photocoagulation in 26 eyes. Follow up was 6 to 30 months. Statistical analysis used Chi-square test, and variance analysis. RESULTS: The overall rate of postoperative PVR was 6.9% (5/72 eyes). The rate of postoperative PVR was 6.5% (3/46) in eyes managed with Argon laser photocoagulation and 7.7% (2/26) in eyes managed with Diode laser photocoagulation (p > 0.05). The rate of postoperative PVR in RD due to horseshoe tears was 5.4% (2/37) in eyes managed with Argon laser and 8.3% (2/24) in eyes treated with Diode laser (p > 0.05). The rate of postoperative PVR in giant tear was 11.1% (1/9) in eyes managed with Argon laser photocoagulation and 0% (0/2) in eyes managed with Diode laser photocoagulation (p > 0.05). CONCLUSION: In the present series the rate of postoperative PVR was not influenced by the method of photocoagulation (transpupillary Argon laser or transscleral Diode laser). Therefore each technique can be used as the retinopexy method in primary rhegmatogenous retinal detachment associated with preoperative grade B PVR.

Adolescent↗
PubMed1997

The basic pattern of activation in motor and sensory temporal tasks: positron emission tomography data.

Positron emission tomography (PET) data were obtained from subjects performing a synchronization task (target duration 2700 ms). A conjunction analysis was run to identify areas prominently activated both in this task and in a temporal generalization task (target duration 700 ms) used previously. The common pattern of activation included the right prefrontal, inferior parietal and anterior cingulate cortex, the left putamen and the left cerebellar hemisphere. These areas are assumed to play a major role in time processing, in relation to attention and memory mechanisms.

Adult↗
PubMed1997

Further argument for the existence of a pacemaker in the human information processing system.

To support the idea that temporal information processing may depend on an internal clock, Treisman et al. proposed a pacemaker model (Treisman, M., Faulkner, A., Naish, P.L.N., Brogan, D., 1990. The internal clock: Evidence for a temporal oscillator underlying time perception with some estimates of its characteristics frequency. Perception 19, 705-743.) and a technique for interfering with it by introducing an external periodic phenomenon. Experimental results obtained by these authors on time estimation and production tasks support this model. In another study, Treisman et al. established that the pacemaker also affects reaction times (RT) (Treisman, M., Faulkner, A., Naish, P.L.N., 1992. On the relation between time perception and the timing of motor action: Evidence for a temporal oscillator controlling the timing of movement. Quarterly Journal of Experimental Psychology 45A, 235-263.). In the present study, we addressed the question as to which information processing stage (Sanders, A.F., 1980. Stage analysis of reaction process, In: Stelmach, G.E., Requin, J. (Eds.). Tutorials in motor behavior. North-Holland, Amsterdam, pp. 331-354.) is affected by this internal clock. For this purpose, we used the Additive Factors Method (Sternberg, S., 1969. The discovery of processing stages: Extension of Donder's method. In: Koster, W.G. (Ed.). Attention and Performance II. Acta Psychologica 30, 276-315.). To vary sensorial processing time, we used two visual stimulus intensities. Stimulus-response mapping was manipulated to enhance central processing time. To modify the duration of the motor stages, the two responses could be given by two fingers on the same hand (right ring vs. middle finger) or by two fingers of the different hands (right ring vs. left middle finger). Intensity of the stimulus, stimulus-response mapping, and repertoire of responses were found to be additive. We obtained RT modulations similar to those obtained by Treisman et al. in 1992. No first order interactions were observed between the periodical phenomenon and the other manipulated factors but only a third order one. Two possible interpretations of these results are proposed.

Adult↗
PubMed1997

Mental simulation of an action modulates the excitability of spinal reflex pathways in man.

The question of whether mental simulation of an action has an effect on the spinal reflex circuits was examined in normal humans. Subjects were instructed either to exert or to mentally simulate a strong or a weak pressure on a pedal with the left or the right foot. Changes in the H- and T-reflexes activated by electrical and mechanical stimuli were measured on both legs during motor performance as well as during mental simulation of the same task. Asynchronous EMG activity of the soleus muscles was simultaneously recorded. Reflex excitability increased during performance of the pressure. It was larger when the H-reflex was triggered in the muscle involved in the task as compared to the contralateral side. Because actual performance modified the tension of the tendon and the location of the stimulus, ipsilateral changes of T-reflex amplitude could not be evaluated. Mental simulation of foot pressure in this condition resulted in a large increase of spinal reflex excitability, which was only slightly weaker than the reflex facilitation associated with the actual performance. Changes in T-reflex amplitude, but not in H-reflex amplitude, depended upon the lateralization and force of the simulated pressure, being larger in the leg involved in the simulation than in the contralateral leg, and larger for a strong than for a weak simulated movement. EMG activity was found to be weakly increased during mental imagery. This increase was significantly, although slightly, modulated by the lateralization and intensity of the imagined movement. However, no correlation was found across subjects between reflex amplitude and the amplitude of EMG activity.

Adult↗
PubMed1997

Contribution to the physically anchored linkage map of the pig.

Thirty-three microsatellites have been mapped on the PiGMaP porcine genetic map. By comparison with the previously published PiGMaP maps, the maps of chromosome 2 (140 cM/70 cM) and chromosome 3 (180 cM/110 cM) were extended and new markers were mapped on the p-arm extremity of chromosome 7 and on the centromeric extremity of chromosome 15. New orders are proposed for markers on chromosomes 3 and 17. Six microsatellites isolated from cosmids were also localized on the cytogenetic map by fluorescent in situ hybridization. We tested the subcloning ligation mixture-polymerase chain reaction (SLiM-PCR) method for isolating microsatellites from cosmids. Subcloning is more effective when the cosmid harbours several microsatellites whereas SLiM-PCR is more straightforward when the cosmid contains a single microsatellite. Fifteen anonymous microsatellites were regionally assigned by using a hybrid cell panel. For map integration, the determination of a regional assignment of anonymous microsatellites by using a hybrid cell panel offers an alternative to microsatellite isolation from cosmids and their localizations by in situ hybridization.

Animals↗