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P Rage

Publications and source records attributed to P Rage.

12 recordsLinked to original sources
PubMed1997

Is the erect posture in microgravity based on the control of trunk orientation or center of mass position?

In the present experiments carried out in microgravity two questions were addressed. First, when the subject was instructed to adopt a vertical erect posture in microgravity with his feet fixed to the floor of the space cabin, would he control anteroposterior position with respect to the ankle joint axis of the "vertical projection" of his center of mass (CM) or trunk axis orientation with respect to the "vertical" (perpendicular to the floor of the space cabin)? Secondly, is CM anteroposterior position regulated during upper trunk movements in microgravity, in the absence of equilibrium constraint? Two subjects were tested in a long-term space flight. Video camera recordings were performed and analyzed off line. The results show that during erect vertical posture in microgravity, the trunk axis with respect to the "vertical" is inclined some 7 degrees forward. The anteroposterior position of the CM "vertical" projection is not shifted forward, as might be expected in view of the trunk inclination, but remains close to the ankle joint axis. At the end of the upper trunk forward or backward bending movement, the final position of the vertical CM projection remains close to the ankle joint axis in microgravity. These results are interpreted as indicating that CM anteroposterior position continues to be accurately controlled in microgravity; the forward inclination of the trunk axis observed in microgravity is interpreted as being due to a misevaluation of the "vertical" axis on the basis of biased information from proprioceptive inputs.

Analysis of Variance↗
PubMed1991

Removal of C6 astrocytoma cell surface molecules with phosphatidylinositol phospholipase C: effect on regulation of neural cell adhesion molecule isoforms.

Different membrane-associated isoforms of the neural cell adhesion molecules have been described. One of them, N-CAM120, has been shown to be anchored to the membranes by a complex glycan-phosphatidylinositol group and to be releasable, under soluble form, by the bacterial enzyme phosphatidylinositol-phospholipase C. We used the C6 rat astrocytoma cell line expressing both N-CAM120 and the transmembrane isoform N-CAM140 as a model system. We investigated whether artificial depletion of cell membrane N-CAM120 influences the synthesis and the messenger RNA transcript levels of the isoforms of the neural cell adhesion molecules. Our results showed an increase in the rate of N-CAM120 protein synthesis, whereas the expression of N-CAM140 decreased. Additionally, perturbations in the levels of the 6.7-kb messenger RNA encoding for N-CAM140 were observed, whereas the 2.7-kb transcript encoding for N-CAM120 remained stable. Examination of the time course for the reexpression of N-CAM120 showed that control levels were recovered after 24 h. We provide evidence that N-CAM120 spontaneously released in the culture medium is not incorporated into the extracellular matrix; however, its concentration is important because, if the medium was changed, cells rapidly released a new pool.

Animals↗
PubMed1990

A new system for computer-assisted quantitative receptor autoradiography.

We have developed a computer-assisted analytic system for quantifying autoradiograms. The system was tested by studying the characteristics of high affinity serotonin binding sites (5-HT1) in rat brain sections, using [3H]5-HT as a radioligand. Autoradiographic data are digitized and transferred to a Macintosh II by means of a high speed, high resolution solid state camera. The physical characteristics of the device (uniformity, temporal stability, linearity) are such that the accuracy of the measurements obtained is highly satisfactory. The autoradiogram grey levels were measured and converted into radioligand concentrations (fmol/mg tissue) with the "BIOLAB" program which was specially written at our department in Macintosh Programming Workshop (MPW). The consistency of the measurements performed on small anatomical structures confirms the reliability of the system. The greatest discrepancies were due to the processing of the sections and also to the biological variability from one animal to another. The low cost of the device described, the high picture definition, the speed with which measurements can be obtained, the reliability of the system, and the original character of the program make it a valuable means to easier analyse quantitative autoradiography in pharmacological and physiological research.

Animals↗
PubMed1989

Changes in exploratory behaviour of hamsters following treatment with 8-hydroxy-2-(di-n-propylamino)tetralin.

The influence of the centrally active 5-HT1A agonist 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) on the exploration of objects was studied in hamsters, using a radioactographic method. This spatial paradigm allows the study of the behavioural expression of underlying locomotor and cognitive (attentional, mnemonic, representative) mechanisms. The drug was found to enhance the cognitive components of the exploratory process, i.e. object-oriented exploration, habituation and, under certain temporal conditions, response-to-change, in a dose-dependent manner. Since drug-injected animals did not differ from controls when no object was present, 8-OH-DPAT probably has no role in non-oriented exploratory activity. The influence of time was further investigated by varying the duration of successive trials and intertrial intervals. In situations where the durations were extremely shortened (3-min trials/3-min intertrial intervals), drug-treated subjects, in contrast to control ones, exhibited a 'hypernormal' time course: they explored and habituated. 8-OH-DPAT appears to increase the efficiency of exploration possibly via a positive effect on arousal or attention. 8-OH-DPAT is assumed to act on 5-HT somatodendritic autoreceptors, lowering 5-HT utilization in the hippocampus, which is the main structure implicated in spatial memory. This exploration paradigm could be employed in the study of time components of environmental adaptation without the need to restrain subjects.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1988

[Effect of ovariectomy and allatectomy on movement of the ovipositor of virgin Acheta domesticus females].

To continuously monitor ovipositor movements a new actograph was devised; it was composed of a radioelement glued at the ventral tip of the ovipositor, a scintillation probe to detect ovipositor movements and a microcomputer to store and process data. Immature and mature virgin females were able to perform ovipositor movements. The removal of the ovaries did not prevent the onset of ovipositor movements. The removal of the corpora allata carried out 6 to 8 days before imaginal moult prevented the onset of these movements. Injections of JH III restored the ovipositor movements previously abolished by allatectomy.

Animals↗
PubMedDate not supplied

Body orientation and center of mass control in microgravity.

The control of the body orientation and the center of mass position with respect to the feet was investigated under normo- and microgravity (space flight Altair), during erect posture and at the end of a forward or backward upper trunk movement. It was observed that during erect posture, the trunk orientation with respect to the vertical was inclined some 6 degrees forward in both subjects under microgravity, whereas it was vertical or slightly backward oriented under normogravity. Under microgravity, on the contrary, the initial position CM changed either backwards or forwards. This result suggests that the inclined trunk posture might be due to misevaluating the verticality under microgravity and that different control mechanisms are involved in orienting the trunk and placing the CM. It was also noted that the final position of the CM at the end of the movement did not differ markedly between microgravity and normogravity. This result suggests that the kinematic synergies which stabilize the CM during upper trunk movements may result from an automatic central control which is independent from the gravity constraints.

Humans↗