Control Levels Of Activity Research Articles

Créativité et formation continue des enseignants

Primary School teachers have seen their profession being transformed over the last few years. The job definition is more opened. By and large, teachers' in- service training is based on formal educational activities and acquisition of teaching knowledge. Furthermore, the training courses on offer are often designed at a higher organizational level. This represents an inadequate response to the new problems than teachers must face on a day-to-day basis. Different actions in teachers' education could be taken, in order to consider an active articulation between different levels of activity control from routine to reinterpretation of elements of reality. This article will focus on a form of training aimed at intermingling the roles and functions of trainers/trainees, while supporting the blending of real world elements in order to improve and develop new practices. Creativity not only implies a cognitive process but also elements of active involvement. As a consequence, teachers are invited to define their own aims and objectives of the training course, the course content and the expected outcomes. This contributes to develop a creative experience. Keywords creativity, teachers training, Primary School, teachers' role, teaching knowledge

Amplitude-dependency of response of SI cortex to flutter stimulation

BackgroundIt is established that increasing the amplitude of a flutter stimulus increases its perceived intensity. Although many studies have examined this phenomenon with regard to the responding afferent population, the way in which the intensity of a stimulus is coded in primary somatosensory cortex (SI) remains unclear.ResultsOptical intrinsic signal (OIS) imaging was used to study the evoked responses in SI of anesthetized squirrel monkeys by 25 Hz sinusoidal vertical skin displacement stimulation. Stimuli were 10 sec duration with a 50 sec inter-stimulus interval. Stimulus amplitude ranged from 50 to 400 microns and different amplitudes were interleaved. Control levels of activity were measured in the absence of stimulation, and used to compare with activation levels evoked by the different stimulus amplitudes. Stimulation of a discrete skin site on the forelimb evoked a prominent increase in absorbance within the forelimb representational region in cytoarchitectonic areas 3b and 1 of the contralateral hemisphere. An increase in stimulus amplitude led to a proportional increase in the magnitude of the absorbance increase in this region of areas 3b and 1 while surrounding cortex underwent a decrease in absorbance. Correlation maps revealed that as stimulus amplitude is increased, the spatial extent of the activated region in SI remains relatively constant, and the activity within this region increases progressively. Additionally, as stimulus amplitude is increased to suprathreshold levels, activity in the surround of the activated SI territory decreases, suggesting an increase in inhibition of neuronal activity within these regions.ConclusionIncreasing the amplitude of a flutter stimulus leads to a proportional increase in absorbance within the forelimb representational region of SI. This most likely reflects an increase in the firing rate of neurons in this region of SI. The relatively constant spatial extent of this stimulus-evoked increase in absorbance suggests that an increase in the amplitude of a 25 Hz skin stimulus does not evoke a larger area of SI neuronal activation due to an amplitude-dependent lateral inhibitory effect that spatially funnels the responding SI neuronal population.

Effects of 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) on locomotor activity and rearing of mice and rats

The effects of 8-OH-DPAT on locomotor activity have not yet been clearly defined. Tricklebank et al. (1984) and Dourish et al. (1985) provide evidence that 8-OH-DPAT increases activity, whereas Mittman and Geyer (1989). Hillegaart et al. (1989) and Carli et al. (1989) suggest that it is reduced by the drug. In the present study, the effects of 8-OH-DPAT on locomotor activity and rearing were examined in habituated and unhabituated mice and rats. The effects of the drug were followed for up to 2 h in the mouse and up to 4 h in the rat. In unhabituated mice and rats, doses of 0.1 mg/kg or more of 8-OH-DPAT blocked activity during the period post-injection when control levels of activity were highest. However, after about 60 min in mice and 150 min in the rat a marked hyperactivity was observed, which was followed by a period of increased rearing. In habituated mice this biphasic effect on locomotor activity was also observed, but there was no increase in rearing. In habituated rats there was no decrease in locomotor activity, rather a biphasic increase was observed. The effects of 8-OH-DPAT on locomotor activity immediately post-injection are interpreted as being a result of the stereotyped, uncoordinated "ambulation" which forms a part of the 5-HT syndrome, and which results in a level of activity intermediate between that of unhabituated and habituated rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Galactose-1-phosphate uridylyltransferase: identification of histidine-164 and histidine-166 as critical residues by site-directed mutagenesis

Galactose-1-phosphate uridylyltransferase catalyzes the interconversion of UDP-glucose and galactose-1-P with UDP-galactose and glucose-1-P by a double-displacement mechanism involving the compulsory formation of a uridylyl enzyme intermediate. The uridylyl group is covalently bonded to the N3 position of a histidine residue in the uridylyl enzyme. The galT gene of Escherichia coli, which codes for the uridylyltransferase and is contained in a plasmid for transformation of E. coli, has been sequenced, and the positions of the 15 histidine residues have been determined from the deduced amino acid sequence of this protein. Fifteen mutant genes, in each of which one of the 15 histidine codons has been changed to an asparagine codon, have been generated and used to transform the E. coli strain JM101. When extracts of the transformants were assayed for uridylyltransferase, 13 exhibited high levels of activity. Two of the extracts containing mutant uridylyltransferase exhibited less than control levels of activity. These mutant proteins, H164N and H166N, were overexpressed, isolated, and tested for their ability to form the compulsory uridylyl enzyme intermediate. Neither the H164N nor the H166N mutant proteins could form the intermediate. Thus, both His-164 and His-166 are critical for activity, and their proximity suggests that both are in the active site. One is the essential nucleophilic catalyst to which the uridylyl group is bonded in the intermediate, and the other serves an equally important, as yet unknown, function. The active-site sequence His(164)-Pro-His(166) is conserved in this enzyme from E. coli, humans, Saccharomyces, and Streptomyces.

Increased protein ADPribosylation in HeLa cells exposed to the anti-cancer drug methotrexate

DNA single-strand breaks (about 200–300 per genome) were transiently detected during the first hour when HeLa cells were incubated for up to 24 h with 100 μM methotrexate. There was an expected increase in ADPribosyltransferase activity, which reached a maximum 2–3-fold stimulation at 3 h but which was still greater than in control cells after 24 h. When hypoxanthine (25 μM) was present in the incubations together with the methotrexate the transferase was no longer activated, although basal, control levels of activity were still present. DNA strand breaks were reduced in number but were still just detectable under these conditions. Cellular NAD + levels were mostly unaffected by the various drug treatments, except for a small transient decrease after 1 h, possibly as a result of the transferase activation. Methotrexate did not cause an increase in the rate of ADPribose degradation. Degradation of ADPribose residues labelled in a preincubation period in permeabilized cells was more extensive at pH 6.0 than at pH 8.0, but was slow relative to other published reports. The maximum rate observed at pH 6.0 was a 50% loss of acid-insoluble radioactivity in 30 min at 26°C. At pH 8.0 the loss did not exceed 30–35% even after 90 min incubation. The activation of the transferase is reflected in a general increase in protein ADPribosylation detected by autoradiography of 32P-labelled proteins in 6.25–18.25%T gradient acrylamide gels. There were three major acceptors with molecular masses of 17, 100 and over 100 kDa, which could be respectively a histone, a transferase-derived peptide fragment and the transferase itself. When ADPribosyltransferase was inhibited with 3-aminobenzamide DNA single-strand breaks were no longer detected. However, this had no observably significant effect on the kinetics of loss of cell viability (from Trypan blue uptake), cell number or colony-forming ability. Similar results are observed in most cases when the activation of the transferase, resulting from the incubation of cells with methotrexate, is inhibited by hypoxanthine. We conclude from such observations that the enhanced protein ADPribosylation seen in the cells exposed to methotrexate is a direct consequence of drug-exposure, but does not have any significant influence over the course of events leading ultimately to cell death.

Changes in alkaline deoxyribonuclease activity in rat liver following partial hepatectomy

The activity of an endonuclease (deoxyribonucleate oligonucleotidohydrolase, EC 3.1.4.5) which preferentially hydrolyses native DNA has been examined during the regeneration of rat liver. The activity of this enzyme increased 2–3-fold prior to the initial post-operative peak of DNA synthesis and remained elevated for at least 70 h. The control levels of activity seen in the sham-operated animals and at 4 h following partial hepatectomy indicate that the observed increase is not due to a shock reaction.

The recovery of liver tetrahydrofolate dehydrogenase activity from inhibition by methotrexate

Rat liver tetrahydrofolate dehydrogenase activity in vivo recovers rapidly from inhibition by methotrexate, despite the known stability of the enzyme-inhibitor complex. Control levels of activity are usually regained within 24 hr following a single injection of methotrexate. A similar pattern of recovery of activity has been found using the Guerin T8 epithelioma. Evidence that the enzyme is actually inhibited in situ has been obtained using a tetrazolium assay system. No evidence could be found for metabolism of the methotrexate to a form inactive with respect to tetrahydrofolate dehydrogenase. Synthesis of new enzyme with retention of the inhibited enzyme did not appear to play a major role in recovery of activity. Experiments using tritiated methotrexate indicated that both in vivo and in vitro, recovery of enzymic activity is probably associated with a dissociation of the enzyme-inhibitor complex.

Comparison of Different Types of Central Stimulation from Analeptics.

1. A method is described for measuring stimulation produced by analeptics, which consists of suspending white rats or other small animals in small cages from wire springs and summating the amount of movement by connecting the springs to Harvard work adders. The activities resulting over periods of hours, are recorded by electrical contacts on the work adders through signal magnets writing on a kymograph drum. The apparatus is kept in a lighted constant temperature chamber between 27 and 29° C as conditions for minimum activity. The amounts of activity shown by the animals after injections of normal saline solution are designated as control levels of activity, and subtracted from those observed during the action of a drug to give the net stimulation produced by the agent in question.