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Biomedical subjects

F Peronnet

Publications and source records attributed to F Peronnet.

At least 19 recordsLinked to original sources
PubMed1997

A macrocyclic bis-acridine shifts the equilibrium from duplexes towards DNA hairpins.

Nucleic acids can undergo dynamic conformational changes associated with the regulation of biological processes. A molecule presenting larger affinities for alternative structures relative to a duplex is expected to modify such conformational equilibria. We have previously reported that macrocyclic bis-acridine binds preferentially to single-stranded regions, especially DNA hairpins, due to steric effects. Here, we show, using gel electrophoresis, fluorescence and melting temperature experiments, that the macrocycle bis-acridine shifts an equilibrium from a duplex towards the corresponding hairpins. Competition experiments enlighten the higher affinity of the macrocycle for hairpins compared with double-stranded DNA. The macrocycle bis-acridine destabilizes a synthetic polynucleotide, by the formation of premelted areas. By extrapolation, the macrocycle bis-acridine should be able to disrupt, at least locally, genomic DNA duplexes and to stabilize unpaired areas, especially palindromic ones forming hairpins. Such macrocyclic compounds may have potential applications in the therapy of diseases involving hairpins.

Acridines↗
PubMed1995

Characterization and cloning of p11, a transrepressor of Drosophila melanogaster retrotransposon 1731.

The NssBF element has been characterized as a 26 nt sequence in the long terminal repeat of Drosophila melanogaster retrotransposon 1731. This sequence has been shown to be implicated in transcriptional repression of the 1731 promoter. We here report the cloning of a cDNA encoding a nuclear DNA binding protein named p11 that binds specifically to the NssBF element. P11 is a 98 amino acid polypeptide. It exhibits similarities with the mouse p9 single-stranded DNA binding protein, raising the possibility of a very general family of protein factors. Co-transfection experiments in human U937 cells showed repression of the 1731 promoter by overexpression of p11.

Amino Acid Sequence↗
PubMed1994

An electrophysiological study of the mental rotation of polygons.

Reaction times and event-related potentials (ERPs) were recorded during a task requiring subjects to decide whether two sequentially presented polygons had the same shape regardless of differences in orientation. Reaction times increased approximately linearly with angular departure from upright orientation, which suggests that mental rotation was involved in the comparison process. The ERPs showed, between 665 and 1055 ms, a late posterior negativity also increasing with angular disparity from upright, which we assumed to reflect mental rotation. Two other activities were exhibited, from 265 to 665 ms, which may be related either to an evaluation of the stimulus or a predetermination of its orientation, and from 1055 to 1600 ms attributed to the decision process.

Adult↗
PubMed1994

A behavioral and electrophysiological study of the comparison of size-discrepant shapes.

An experiment was performed to find an electrophysiological correlate of the way objects of different sizes are perceived as identically shaped. The subjects were presented with pairs of geometrical figures and were instructed to decide whether the two polygons of a pair were identical in shape regardless of size. In addition to event-related potentials (ERPs), reaction times and error rates were recorded. Reaction times increased approximately linearly with increasing size ratios. The subtraction between the ERPs of 'test' and 'control' conditions showed two main activities: a positivity localized on the occipitotemporal scalp areas in the 200-450 ms range, and a negativity localized on the posterior scalp areas in the 500-750 ms range. These different results were discussed with respect to size ratio.

Adolescent↗
PubMed1994

Mental rotation and mirror-image discrimination.

Two experiments involving judgments of same-different were conducted to assess conditions in which mental rotation is used. These two experiments were similar except in the way "different" pairs were constructed. In the first experiment, a "different" pair involved two different polygons; in the second one, a "different" pair involved one polygon and its mirror-image. The strategy used by the 8 subjects was investigated through patterns of reaction times. The first experiment exhibited a flat function of reaction times with orientation, whereas the second one exhibited a linear increase in reaction times with angular departure from upright. These results lead to the conclusion that mental rotation is used when a figure has to be distinguished from its mirror-image.

Adult↗
PubMed1989

Mental rotation: an event-related potential study with a validated mental rotation task.

Event-related potentials (ERPs) were recorded while subjects performed a validated mental rotation task, taken from the cognitive psychology literature. These ERPs show a late posterior negativity relative to a baseline condition requiring all of the same perceptual and cognitive processes except for the mental rotation itself. Our tentative identification of this posterior negativity with mental rotation is further supported by the finding that it varies systematically with the amount of mental rotation required on a trial by trial basis in the experimental task. We conclude that this late negativity is an ERP marker of the mental rotation process, and that this process engages primarily posterior brain regions.

Arousal↗
PubMed1989

Oxidation of corn starch, glucose, and fructose ingested before exercise.

The purpose of this study was to compare the metabolic and endocrine responses, and the amounts of exogenous carbohydrate oxidized, during prolonged moderate cycle ergometer exercise (120 min, 60% VO2max), preceded by ingestion of 13C enriched glucose (G), fructose (F), or pure corn starch (S) (1,592 kJ ingested with 400 ml of water, 60 min before the beginning of exercise) in six healthy young male subjects. Plasma glucose and insulin concentrations significantly increased in response to G and S feeding. The high plasma insulin values resulted in a significant transient reduction in plasma glucose concentration in the first hour of exercise and blunted the response of plasma free fatty acid and glycerol concentrations, when compared to the values observed with F ingestion, which did not modify plasma glucose or insulin concentrations. Over the 2 h exercise period, the percentages of exogenous G (67 +/- 9%) and S (73 +/- 8%) oxidized were not significantly different but were significantly higher than the percentage of exogenous F oxidized (54 +/- 6%). These results confirm that 1) exogenous F is less readily available for oxidation than G or S and 2) pure corn starch does not offer any advantage over glucose as a pre-exercise meal.

Adult↗
PubMed1988

Several attention-related wave forms in auditory areas: a topographic study.

The purpose of this study was to progress in the understanding of the electrogenesis of attention-related wave forms in order to highlight some of the underlying attentional processes. ERPs were recorded from 16 electrodes, from 12 subjects who attended selectively to either high or low pitch tones delivered at a constant inter-stimulus interval of 800 msec to either right or left ear, while ignoring a concurrent sequence of tones of the other pitch delivered to the other ear. The attention-related wave forms were obtained by subtracting ERPs to unattended tones from ERPs to the same tones when they were attended. These wave forms were topographically displayed by both potential maps and scalp current density maps and compared with the corresponding maps of the N1 component of the ERPs, to determine the similarity of their generators. It has been shown that the attention effect is expressed by at least two components in specific auditory areas, one of small amplitude, occurring during the ascending slope of the N1 component, sensitive to the pitch of the attended stimulus, and possibly originating in the supratemporal plane of the auditory cortex; another of large amplitude, peaking symmetrically over both hemispheres and having a different topography from that of the N1 component. As described by other authors, a third, later, component appears over frontal areas, but probably originates from deeper sources of the brain. Models of selective attention processes, particularly the 'attentional trace' concept, are discussed in the light of these results.

Adult↗
PubMed1988

Failure to alter sympathoadrenal response to psychosocial stress following aerobic training.

This experiment assessed the impact of aerobic training on sympathoadrenal, heart rate and subjective responses to psychosocial stress. Subjects were six previously sedentary males who demonstrated marked improvement in fitness level following 10 weeks of training. Plasma samples, heart rate and subjective arousal ratings were obtained prior to, during, and following exposure to stressful mental tasks within a laboratory session. With the exception of training-related bradycardia which was manifest throughout the session, no changes in plasma epinephrine and norepinephrine concentrations, heart rate or subjective reactivity or recovery were seen. These findings are inconsistent with the hypothesized beneficial effects of aerobic training on stress-response. Methodological factors such as self-selection inherent in previous correlation work or the duration of the training program should be considered in this context. The potential contribution of training-related bradycardia to enhanced coping with challenging situations is explored.

Adult↗
PubMed1988

Dexamethasone stimulates expression of transposable type A intracisternal retroviruslike genes in mouse (Mus musculus) cells.

Dexamethasone treatment enhances expression of transposable intracisternal type A particles (IAP) at RNA and proteins levels in a murine retrovirus-transformed cell line (Ki-BALB). This effect was ascertained by electron microscopic numeration of IAP. By sequence comparison, we located glucocorticoid-responsive elements in IAP long terminal repeats. Their regulatory potential was tested on the promoter activity of an IAP long terminal repeat construct coupled with the chloramphenicol acetyltransferase gene. Our findings suggest that the IAP activation by dexamethasone occurs at the level of transcription.

Animals↗
PubMed1987

Fluid-electrolyte shift and renin-aldosterone responses to exercise under hypoxia.

In order to describe fluid-electrolyte shift and endocrine response to exercise under moderate acute hypoxia, 8 healthy male subjects (24 +/- 3 years old) were evaluated at 40, 60, 80 and 100% VO2 max in normoxic (N) and hypoxic (H) conditions (14.5% O2). VO2 max decreased from 55.5 +/- 1.3 to 45.8 +/- 1.4 ml/kg X min in H condition. Plasma volume reductions with increasing relative workloads were similar in N (9.4%) and H (9.9%) conditions. The rise in plasma osmolality was in part related to blood lactate accumulation which occurred in both conditions. However, variations in plasma solute content and osmolality suggested that exercise under hypoxia results in a greater electrolyte loss from vascular space and in a greater K+ loss from working skeletal muscles. Increase in catecholamine concentrations were similar in normoxic and hypoxic conditions except for lower maximal norepinephrine concentration under hypoxia. Finally, although plasma renin activity increased with workload in both conditions, plasma aldosterone did not significantly change. This dissociation between renin and aldosterone suggest that aldosterone release during exercise might depend upon other factors. However, changes in plasma potassium concentration do not appear as an important stimulus for aldosterone secretion during exercise.

Adult↗
PubMed1986

1731, a new retrotransposon with hormone modulated expression.

We report here the characterisation of 1731, a new copia-like element of Drosophila melanogaster. 1731 was first isolated in a screening for ecdysterone modulated genes. This element is about 4.6 Kb long and is flanked by two long terminal repeats (LTRs) 336 base pairs in length. The whole 1731 element is transcribed into polyA+ RNAs, and these transcripts decrease rapidly upon hormonal treatment. 1731 is moderately repeated in the fly genome and slightly amplified in Kc/cells where extrachromosomal circular forms are found. The LTRs were sequenced in one cloned copy of 1731 and show a structural organisation similar to that of several other copia-like elements and retroviral proviruses. Small nucleotide stretches, similar to those found in Mouse Mammary Tumor Virus LTRs and known to be important in its regulation by a steroid hormone, occur in 1731 LTRs.

Animals↗
PubMed1986

Systemic and regional blood flows during graded treadmill exercise in dogs.

The purpose of the study was to describe hemodynamic response and regional blood flows through various organs and tissues (microsphere technique) in dogs (n = 8), at rest and during mild (4 km/h, 13% slope; heart rate = 154 bpm), moderate (4 km/h, 26% slope; heart rate = 201 bpm), and severe (4 km/h, 39% slope; heart rate = 266 bpm) exercise on treadmill. Cardiac output (rest: 3.2 +/- 0.3; 39% slope: 10.2 +/- 1.3 l/min; mean +/- SE), systolic aortic pressure (rest: 122 +/- 4; 39% slope: 158 +/- 9 mm Hg), and left atrial pressure (rest: 5 +/- 0.7; 39% slope: 11.0 +/- 0.6 mm Hg) increased linearly with workload. On the contrary stroke volume increased from rest (35 +/- 2 ml) to mild (38 +/- 2 ml) and moderate (42 +/- 3 ml) exercise but decreased in response to the severe workload (38 +/- 5 ml). Regional blood flows across the brain, femoral bone, adrenal glands and temporalis muscle were not modified during exercise. On the contrary, a marked increase in regional blood flow was observed through the flexor and extensor muscles of the limb (X 5 to X 15), the muscles of the back (X 4) and the diaphragm (X 2.5). The small inconsistent increase in nutritional tongue blood flow probably underestimated the increased perfusion through arteriovenous shunts in the mucosa for heat-loss purposes. Myocardial blood flow increased in a linear fashion with work load in both ventricles.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Effects of posterior parietal lesions on visually guided movements in monkeys.

Four monkeys were trained to position, with either hand, a vertical rod in front of one of 5 target lights spaced 20 degrees apart on a semicircular screen. After the monkeys had reached the preoperative criterion (80% trials correct per session) they received a 1- or 2-stage bilateral lesion of posterior parietal cortex restricted to area 7. The lesion produced in all the monkeys considerable but temporary changes in movement latency, accuracy, velocity and duration. Latency increase appeared to be independent of changes in the other parameters. After the first lesion, movement latency increased for the contralateral arm in both left and right working spaces, from 100 ms up to 400 ms depending on the animal. A second lesion symmetrical to the first one increased movement latency of the arm contralateral or ipsilateral to the last lesion, depending on the time interval between the two lesions. In addition, unilateral lesions of area 7 induced a gross inaccuracy in movements of the arm contralateral to the lesion, more marked in the contralateral working space. These lesions also increased movement peak velocity and simultaneously decreased movement duration for the arm contralateral to the lesion. The increase in velocity appeared to be related to the decrease in duration. A second lesion of area 7 in the opposite hemisphere similarly affected accuracy, velocity and duration but for the arm contralateral to the second lesion.

Animals↗
PubMed1985

Sympathetic indices during psychological and physical stimuli before and after training.

The effects of psychological and physical stimuli on cardiovascular and catecholamine changes were studied before and after physical training. These functions were investigated in eight labile hypertensive men in response to the mild psychological stimulus of playing a video game and the mild physical stimuli of sitting and standing. The results show that plasma norepinephrine concentration rises with sitting and standing but plasma epinephrine concentration increases only with the psychological stimulus. Physical training was associated with smaller increases in blood pressure during psychological and physical stimuli and with a lower heart rate at rest. On the other hand, plasma catecholamines at rest as well as in response to the different stimuli were unchanged following moderate training. These observations suggest that the adrenal medulla is selectively activated during a period of mild psychological stress, while the activity of the sympathetic fibers is preferentially increased during mild physical stimuli. Furthermore, the results of this study show that plasma catecholamine levels at rest and their increase during various stimuli are unchanged following training.

Adult↗
PubMed1985

Sequential colour mapping system of brain potentials.

We present a colour mapping system for the visualization of both the spatial scalp distribution and the temporal evolution of brain potentials. The system is applicable to recordings of auditory, visual and somatosensory potentials. It uses a Tektronix 4113 colour terminal connected to a Solar 16 (SEMS) mini-computer. The brain potentials are recorded on up to 16 scalp electrodes. The gain and the baseline are corrected separately on each channel. At each point of the scalp the potential is reconstructed by a linear interpolation of the measured potentials of the four nearest electrodes. Simultaneously n2 (1 less than n less than 8) colour maps can be presented on the screen. This allows the study of the temporal evolution of full scalp evoked potentials. The user chooses the two extreme latencies defining the time window to be explored and the latencies of the maps are regularly time-spaced within this window. In a typical case, in which four maps are desired, the latencies of the maps can be chosen independently. The 16-colour palette is predetermined but the user has three possibilities to establish the correspondence between the electrical potential and the colours. Examples are shown in the visual and somatosensory stimulation modalities. The advantages and limitations of such a representation are discussed.

Brain↗