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C Collet

Publications and source records attributed to C Collet.

At least 19 recordsLinked to original sources
PubMed1999

Intracellular calcium signals measured with indo-1 in isolated skeletal muscle fibres from control and mdx mice.

1. Intracellular free calcium concentration ([Ca2+]i) was measured with the fluorescent indicator indo-1 in single skeletal fibres enzymatically isolated from the flexor digitorum brevis and interosseus muscles of control and dystrophic mdx C57BL/10 mice. Measurements were taken from a portion of fibre that was voltage clamped to allow detection of depolarization-induced changes in [Ca2+]i. 2. The mean (+/- s.e.m.) initial resting [Ca2+]i from all control and mdx fibres tested was 56 +/- 5 nM (n = 72) and 48 +/- 7 nM (n = 57), respectively, indicating no significant overall difference between the two groups. However, when comparing a batch of control and mdx fibres obtained from mice older than approximately 35 weeks, resting [Ca2+]i was significantly lower in mdx (16 +/- 4 nM, n = 11) than in control fibres (71 +/- 10 nM, n = 14). 3. Changes in [Ca2+]i elicited by short (5-35 ms) depolarizing pulses from -80 to 0 mV showed similar properties in control and mdx fibres. After a 5 ms duration pulse the mean time constant of [Ca2+]i decay was, however, significantly elevated in mdx as compared to control fibres, by a factor of 1.5-2. For longer pulses, no significant difference could be detected. 4. In response to 50 ms duration depolarizing pulses of various amplitudes the threshold for detection of an [Ca2+]i change and the peak [Ca2+]i reached for a given potential were similar in control and mdx fibres. 5. Overall results show that mdx skeletal muscle fibres are quite capable of handling [Ca2+]i at rest and in response to membrane depolarizations.

Age Factors↗
PubMed1999

Autonomic nervous system responses as performance indicators among volleyball players.

Complex motor skills require planning and programming before execution. The autonomic nervous system (ANS) is thought to transcribe these central operations at the peripheral level: a motor act is thought to be simultaneously programmed by central and autonomic nervous structures. The aim of this study was to verify that autonomic responses reflect the quality of central motor programming leading to successful or failed performance when subjects are required to perform a complex motor skill. The specificity of the ANS response has already been demonstrated through direct recording from sympathetic fibres. It has also been demonstrated through several mental tasks and closed motor skills such as shooting: ANS responses have been shown to be capable of distinguishing success from failure. The aim of this experiment was to test whether ANS responses are capable of distinguishing two levels of achievement during the performance of a skill involving uncertainty (open skill). The subjects had to intercept a ball on a volleyball court, using the forearm receive and pass technique, in order to pass it on to a moving human target. The results were displayed in terms of accuracy: accurate passes were successful and inaccurate passes missed the target. Six autonomic variables were recorded simultaneously during the task: skin resistance and potential, skin blood flow and temperature, instantaneous heart rate and respiratory frequency. Results showed that autonomic variables were capable of distinguishing success from failure in 22 subjects out of 24. This made it possible to build up autonomic patterns characterising subjects' performances, and to confirm that autonomic functioning may reveal information processing in the central nervous system. Thus, the study of autonomic responses may constitute an inferential model of central nervous system functioning. Such a method could be used as an index for the control of mental preparation.

Adult↗
PubMed1999

Imagery quality estimated by autonomic response is correlated to sporting performance enhancement.

It is now well established that mental imagery practice improves motor skills, but performance efficiency depends on many factors: the main one being individual differences. The aim of this study is to evaluate performance improvement with imagery quality estimated during ANS recording. Volleyball training ("receiving serve") afforded us the experimental paradigm. Subjects were required to pass an opponent's serve to a given team mate. The receiver's performance was evaluated from the accuracy of his pass to the targeted team mate. From these first test results, subjects were divided into two equivalent groups: imagers and controls. After mental practice the two groups were submitted to a posttest similar to the first one. During the pretest, posttest actual practice as well as the last session of corresponding mental rehearsal, six autonomic parameters were continuously recorded. Furthermore, and for the first time, a grade obtained from four different aspects of this response permits qualitative evaluation of each subject's mental imagery. This estimation, based on the well-established link between performance and autonomic response, is validated by the fact that good correlation was obtained between this grade and the performance improvement of each of the "imager" group subjects.

Adult↗
PubMed1999

Programming or inhibiting action: evidence for differential autonomic nervous system response patterns.

In the general context of decision-making analysis, the aim of this study was to investigate autonomic nervous system activity when movement execution is inhibited just before onset. Using a 'Go/NoGo' paradigm, 16 subjects (nine males and seven females) had to intercept green table-tennis balls thrown by a robot, with the inner side of their hand and by arm extension. Conversely, they had to inhibit movement programming when a red ball was thrown. Results were displayed in terms of success or failure in view of the aim of each trial. Electrodermal, thermo-vascular and cardio-respiratory parameters were continuously recorded from the non-dominant hand. Results showed that the duration of autonomic responses was significantly longer in action than in inhibition. Temperature responses were negative but significantly more marked in action. Instantaneous respiratory frequency amplitude responses were positive in both action and inhibition conditions, but higher in action. Instantaneous heart rate responses confirmed that inhibition elicits cardiac deceleration. Autonomic responses were shown capable of distinguishing action from inhibition, thus reflecting central nervous system functioning. Results are discussed in terms of autonomic response specificity.

Adult↗
PubMed1999

Neuroanatomical correlates of visually evoked sexual arousal in human males.

Brain areas activated in human male sexual behavior have not been characterized precisely. For the first time, positron emission tomography (PET) was used to identify the brain areas activated in healthy males experiencing visually evoked sexual arousal. Eight male subjects underwent six measurements of regional brain activity following the administration of [15O]H2O as they viewed three categories of film clips: sexually explicit clips, emotionally neutral control clips, and humorous control clips inducing positive but nonsexual emotions. Statistical Parametric Mapping was used to identify brain regions demonstrating an increased activity associated with the sexual response to the visual stimulus. Visually evoked sexual arousal was characterized by a threefold pattern of activation: the bilateral activation of the inferior temporal cortex, a visual association area; the activation of the right insula and right inferior frontal cortex, which are two paralimbic areas relating highly processed sensory information with motivational states; and the activation of the left anterior cingulate cortex, another paralimbic area known to control autonomic and neuroendocrine functions. Activation of some of these areas was positively correlated with plasma testosterone levels. Although this study should be considered preliminary, it identified brain regions whose activation was correlated with visually evoked sexual arousal in males.

Adult↗
PubMed1999

Luteinizing hormone measurement in polycystic ovary syndrome: a practical approach.

The biological diagnosis of polycystic ovary syndrome (PCO) remains questionable, and a single immunological hLH (ihLH) determination can be misleading. In order better to characterize these patients, we studied hLH pulsatility every 10 min for 4h using a radioimmunoassay and then compared the results with others we obtained with a biological method. Radioimmunological and biological profiles were similar in patients with PCO and in controls. We also studied pulsatility characteristics - frequency and amplitude - and calculated the area under the curve (AUC). There was no significant increase in frequency in our 10 patients with PCO but, as in other studies, increased amplitude of hLH pulses was observed. The most discriminating parameter was the AUC. For practical purposes, we propose that hLH in patients with PCO could be assessed efficiently by taking four samples every 10 min, with computerized calculation of the AUC.

Adolescent↗
PubMed1999

Strategic aspects of reaction time in world-class sprinters.

Simple reaction time (RT) is defined as the time duration following the initiation of a stimulus and the resultant first observable response. For sprinters, RT to a start should be especially important, as this may determine the outcome of the race. The aim of this study was to investigate whether sprinters (from 100 to 400 m) try to anticipate the starter's shot within the false start limit (100 msec. after the shot). Subjects were male sprinters who have reached the final of a sprint event in World Championships or Olympic Games. Analysis indicated that RT to the starting shot plays a role in the eight finalists' strategy throughout an event (requiring a total of four sprints). Four characteristics of the strategic aspects of RT were found: (i) Increased mean RT from short dashes to longer sprints (from 60 m indoor, to 100 m, 200 m, and 400 m); (ii) RT values increase as a function of race length, i.e., the RT of the first sprinter in a 4 x 100-m relay is no different from that of a 400-m sprinter; conversely, RT of the first relay sprinter in a 4 x 400-m, i.e., a 1600-m race, is significantly different from RT in a 400-m race; (iii) RT decreases from the heats to the final for the eight finalists; (iv) Decreased RT is not observable in less experienced sprinters through the qualifying rounds (junior 18- or 19-yr.-old sprinters, taking part in their own World Championships). RT must be considered a skill dependent upon experience and learning and is associated with race length. The shorter the race, the more important the RT is for the final performance (both time and place), so sprinters try to decrease RT in the shorter dashes (60 m and 100 m). In the longer sprint races (4 x 400-m relay) they are content to respond to the shot. Intermediate distance races elicit intermediate values of RT. Such behavior could be explained by the importance of RT throughout the factors which influence sprint performance and by reference to allocation of concentration resources and expenditure.

Acoustic Stimulation↗
PubMed1998

How many insulin-like growth factor binding proteins?

Mac25, connective tissue growth factor, the nov-oncogene and cyr61 have been proposed as insulin-like growth factor binding proteins (IGFBPs) although they bind the ligand with very low affinity. Sequence similarity between the candidate proteins and the recognised IGFBPs is restricted to a single cysteine-rich N-terminal domain. The cysteine-rich domain (CRD) can be found in other vertebrate and invertebrate proteins that are associated with the extracellular matrix but otherwise have vastly different functions. Characteristically, the proteins with the CRD have a modular architecture suggesting that exon shuffling has played a significant role in their evolution. Although the proposed candidate proteins may not be IGFBPs, linkage relationships of the latter suggest that two other IGFBPs may indeed exist.

Amino Acid Sequence↗
PubMed1998

Autonomic nervous system responses correlate with mental rehearsal in volleyball training.

The aim of this study was to assess objectively the processes of mental rehearsing (imagery) by measuring variations of the autonomic nervous system (or ANS responses) during an open-ended complex motor skill in two actual experiments (volleyball) and during mental rehearsing taking place between them. Comparison between pre- and post-test (volleyball) scores related to imagining and non-imagining performances revealed significant improvement in the former (chi2 = 20.9, P < 0.00001) while in the latter chi2 = 27, P < 0.9, NS. The ANS parameters (skin potential and resistance, skin temperature and heat clearance, instantaneous heart rate and respiratory frequency) were quantified by original techniques and indices. Results from a principal component analysis showed a strong correlation between the responses in actual tasks (pre- and post-test volleyball) and during mental imagery, since the same preferential variables appeared on the main axis in 87% of cases. Thus the same autonomic channels seemed to be used during the actual activity and during the mental imagery of this activity. So far as phasic results were concerned, the main finding was a differing development of skill between imagining and non-imagining volleyball players. No clear difference was seen between pre- and post-tests in non-imaginers, except an increase in the median of the duration of the response observed in heat clearance, m1 and m2 respectively [m1 = 5.8 (SD 4.1) s, m2 = 7.6 (SD 3.9) s, P < 0.001]. Conversely, for other ANS parameters, a significant decrease was seen in the post-test responses compared to pre-test responses in the imagining group [for instance, the median of the duration of the resistance responses decreased from m1 = 12.6 (SD 4.3) s, and m2 = 7.8 (SD 4.5) s, P < 0.0001 in imaginers, while no change was observed in non-imaginers: 9.6 (SD 6.0) s vs 9.5 (SD 6.1) s, NS] except in the duration of the heat clearance response where an increase was seen [m1 = 7.3 (SD 5.0) s vs m2 = 7.6 (SD 3.1) s, NS]. Compared to the non-imagining group, the latter result may also have been associated with a response decrease in the imagining group. Thus mental rehearsing induced a specific pattern of autonomic response: decreased amplitude, shorter duration and negative skin potentials compared to the control group. As this pattern was associated with better performance in the tests it can be suggested that in the case of open-ended motor activity, mental rehearsing may help in the construction of schema which can be reproduced, without thinking, in actual practice. Thus a neural information process might develop in the central nervous system changing from a parallel into a serial treatment.

Adult↗
PubMed1998

The phylogeny of the insulin-like growth factors.

The insulin-like growth factors are major regulators of growth and development in mammals and their presence in lower vertebrates suggests that they played a similarly fundamental role throughout vertebrate evolution. While originally perceived simply as mediators of growth hormone, on-going research in mammals has revealed several hierarchical layers of complexity in the regulation of ligand bioavailability and signal transduction. Our understanding of the biological role and mechanisms of action of these important growth factors in mammals patently requires further elucidation of the IGF hormone system in the simple model systems that can be found in lower vertebrates and protochordates. This review contrasts our knowledge of the IGF hormone system in mammalian and nonmammalian models through comparison of tissue and developmental distributions and gene structures of IGF system components in different taxa. We also discuss the evolutionary origins of the system components and their possible evolutionary pathways.

Amino Acid Sequence↗
PubMed1998

Tyrosine hydroxylase and insulin-like growth factor II but not insulin are adjacent in the teleost species barramundi, Lates calcarifer.

In humans, the genes encoding tyrosine hydroxylase (TH), insulin and insulin-like growth factor II (IGF-II) form an extremely tight linkage group on chromosome 11p15. Characterisation of the homologous genomic region of a teleost, the barramundi Lates calcarifer, revealed tight linkage of the TH and IGF-II genes, and the absence of the gene encoding insulin.

Animals↗
PubMed1997

Lysozyme and alpha-lactalbumin from the milk of a marsupial, the common brush-tailed possum (Trichosurus vulpecula).

Lysozyme and alpha-lactalbumin have been identified using N-terminal sequence analysis of whey proteins from the common brush-tailed possum, Trichosurus vulpecula after separation by two-dimensional denaturing electrophoresis. Both proteins were purified from pooled possum milk using ion exchange chromatography and gave mass values of 14,896 and 13,985 Da respectively by MALDI-TOF mass spectrometry. Clones containing the full coding sequences of the genes for both proteins were isolated from a possum mammary cDNA library and the DNA sequence of the coding region determined. The inferred protein sequences were used in phylogenetic analysis of both protein classes. These showed that the T. vulpecula alpha-lactalbumin, along with other marsupial alpha-lactalbumins, formed a family distinct from the eutherian alpha-lactalbumins and the alpha-lactalbumin of a monotreme, the platypus, consistent with the separate evolution of the marsupials. By contrast the T. vulpecula lysozyme was shown to be similar to the ruminant stomach lysozymes and primate lysozymes and quite distinct from the Ca2+-binding lysozymes found in the milk of the echidna and horse.

Amino Acid Sequence↗
PubMed1997

Reliability of tuberculin skin test measurement.

BACKGROUND: Important management decisions depend on results of the tuberculin skin test. However, the test is subject to several potential errors, and its reliability has not been adequately studied. OBJECTIVE: To ascertain the reliability of tuberculin skin testing. DESIGN: Cross-sectional study. SETTING: University hospital. PARTICIPANTS: 96 persons who received a tuberculin skin test. MEASUREMENTS: Ballpoint-pen and palpation measures of induration. RESULTS: Global intra- and interobserver reliability coefficients of the ballpoint-pen technique were high. Five percent of the time, however, a second measurement by the same observer could be at least 2.7 mm less to 3.0 mm more than the first measurement and the measurement from the second observer could be at least 3.4 mm less to 3.7 mm more than the measurement from the first observer. This could lead to the reclassification of a positive test result as negative or vice versa. The area of imprecision was 38% less broad for the ballpoint-pen technique than for the palpation technique. CONCLUSION: Reading of tuberculin skin tests may frequently result in misclassifications when measurements are close to the cutoff point that separates negative from positive results.

Cross-Sectional Studies↗
PubMed1997

Autonomic nervous system response patterns specificity to basic emotions.

The aim of this study was to test the assumption that the autonomic nervous system responses to emotional stimuli are specific. A series of six slides was randomly presented to the subjects while six autonomic nervous system (ANS) parameters were recorded: skin conductance, skin potential, skin resistance, skin blood flow, skin temperature and instantaneous respiratory frequency. Each slide induced a basic emotion: happiness, surprise, anger, fear, sadness and disgust. Results have been first considered with reference to electrodermal responses (EDR) and secondly through thermo-vascular and respiratory variations. Classical as well as original indices were used to quantify autonomic responses. The six basic emotions were distinguished by Friedman variance analysis. Thus, ANS values corresponding to each emotion were compared two-by-two. EDR distinguished 13 emotion-pairs out of 15. 10 emotion-pairs were separated by skin resistance as well as skin conductance ohmic perturbation duration indices whereas conductance amplitude was only capable of distinguishing 7 emotion-pairs. Skin potential responses distinguished surprise and fear from sadness, and fear from disgust, according to their elementary pattern analysis in form and sign. Two-by-two comparisons of skin temperature, skin blood flow (estimated by the new non-oscillary duration index) and instantaneous respiratory frequency, enabled the distinction of 14 emotion-pairs out of 15. 9 emotion-pairs were distinguished by the non-oscillatory duration index values. Skin temperature was demonstrated to be different i.e. positive versus negative in response to anger and fear. The instantaneous respiratory frequency perturbation duration index was the only one capable of separating sadness from disgust. From the six ANS parameters study, different autonomic patterns were identified, each characterizing one of the six basic emotion used as inducing signals. No index alone, nor group of parameters (EDR and thermovascular for instance) were capable of distinguishing each emotion from another. However, electrodermal, thermo-vascular and respiratory responses taken as a whole, redundantly separated each emotion thus demonstrating the specificity of autonomic patterns.

Adult↗
PubMed1997

Organization, sequence, and expression of the gene encoding IGFII from barramundi (Teleosteii; Lates calcarifer).

We have characterized the gene encoding IGFII from the teleost fish species barramundi, Lates calcarifer. The barramundi gene spans 5.5 kb of DNA and comprises four exons and three introns. The barramundi and salmon IGFII genes share > 85% sequence similarity across all the exons and also share some regions of high sequence identity within the promoter regions and the introns. The mature barramundi IGFII peptide comprises 70 amino acid residues and shares 84 and 96% similarity with salmonid and seabream IGFII, respectively, with the majority of replacements located in regions cleaved from the mature peptide. IGFII mRNA transcripts were detected in liver, muscle, intestine, gill, heart, and brain from juvenile barramundi. This distribution mirrors that seen in the rainbow trout and seabream and extends the tissue types which synthesize IGFII in fish to include the intestine.

Amino Acid Sequence↗