Comparaison des modeles de neurone de Hodgkin-Huxley et de Nelson

Le modèle de Nelson peut-être considéré comme une approximation du modèle de Hodgkin-Huxley. Moins précis, il est plus maniable. Le modèle de Nelson peut également être considéré comme une généralisation du modèle de Hodgkin-Huxley. En effet, il introduit des liaisons synaptiques localisées ou diffusantes, et un processus de facilitation. Le mécanisme des liaisons synaptiques ne se traduit pas facilement dans le langage de Hodgkin-Huxley. Par contre, le processus de facilitation s'interprète facilement. Nelson's model can be taken as an approximation of Hodgkin-Huxley's model. Its precision is lesser, but it is more usable. Nelson's model can also be taken as a generalization of Hodgkin-Huxley's one; for it introduces localized or diffusing synaptic connexions and a facilitating process. The mechanism of synaptic connexions cannot be easily translated into Hodgkin-Huxley's language. On the contrary, the facilitating process is easily interpreted.      

A Propos de la Comparaison Graphique des Matrices de Variance

We compare variance-covariance matrices considered as matrices of similarities between variables. The first part recalls the mathematical bases of the proposed method. The second part treats a set of meteorological data.     

Comparaison de la dose efficace en TEP/TDM et en TDM

Hybrid imaging, particularly positron emission tomography (PET) combined with CT has emerged in the field of oncology as a modality of choice. The concomitant realization of a standard CT examination, however, raises the question of the additional dose delivered to the patient. This radiation burden could be avoided by performing a single PET/CT examination with injection of contrast media. To verify the potential dosimetric gain of this strategy, we compared the effective dose associated with each modality in a retrospective cohort of 151 patients, homogeneous in weight and size. The average effective dose for a PET/CT (injection of 5-6 MBq/kg of ¹⁸FDG) was 13.5 mSv, the CT dose representing approximately 80% of the PET dose. In our study, the average effective dose in CT thorax/abdomen/pelvis was 21.4 mSv, 60% higher than the PET/CT effective dose.     

Analyse de la structure fine des chromosomes du Gorille (Gorilla gorilla)

Summary Prometaphasic chromosomes of Gorilla, Homo and Pan are compared, using R, Q, T and H-bands techniques in complement of a previous work (Lejeune et al., 1973). Various mechanisms of chromosomal rearrangements are demonstrated with particular reference to heterochromatic segments. Some phylogenic conclusions are proposed.

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Zusammenfassung Prometaphase-Chromosomen von Gorilla, Mensch und Schimpanse werden mit hilfe der R-, Q-, T- und H-Bandentechnik verglichen; frühere Arbeiten (Lejeune et al., 1973) werden dadurch ergänzt. Verschiedene Mechanismen von Chromosomen-Rearrangements werden dargestellt; dabei finden die Heterochromatin-Segmente besondere Beachtung. Einige phylogenetische Folgerungen werden gezogen.

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Travail de l'E.R.A. n^o 47 du C.N.R.S.     

Action de l'antimycine A sur la respiration et la structure des mitochondries d'Euglena gracilis Z.

Summary Addition of antimycin A to a culture of Euglena gracilis Z growing with lactate causes an immediate increase of respiration, through a pathway not inhibited by cyanide. Several hours after antimycin addition, giant mitochondrion develop. They are easily observable in the light microscope after staining with a tetrazolium salt; and electron microscopy reveals that they have a ramified structure, with a matrix containing many cristae.     

La symbiose du spermatozoide et de l'ovule,origine de l'ontogenese et de la phylogenese des metazoaires

The origin of metazoa implies the passage from an eukarote protozoan to a protozygote ancestor of a metazoan zygote. The most probable hypothesis is that of a symbiotic origin of the first zygote by association of two protists one signifying a spherical oocell and the other a flagellated spermatozoan; this could be the first step of the metazoan ontogenesis and therefore also of the phylogenesis. The genesis can also be explained by two haploid genomes NX NY, three gametes (two spermatozoa and one ovule), NX apparently being able to create both forms, and two zygotes. A double symbiosis, a chromosomic crossing-over and a selective expulsion can prove it.     

Comparaison paléocognitive des niveaux moustérien et magdalénien de la grotte Tournal (Bize, Aude)

We analyse the functional processing chain of large mammals acquired at the mousterian and magdalenian levels of the Tournal cave (Bize, Aude). Palethnologic results are analysed through a method from experimental psychology of goal oriented activities. The elements are the objects used by prehistoric man and their properties. Objects and properties are linked by binary relationships. These relationships are processed by software, SIMBOL, developed at the IPH, based on an algorithm initially published by the Laboratoire de psychologie expérimentale of Paris-8. SIMBOL returns the cognitive graph of the task representation for the mousterian and the magdalenian layer, allowing a rigorous comparison of the cognitive activities on both periods. The main result is that the logical structure is preserved when passing from one level to the other. This could be interpreted as a due to the noticeable cognitive similarity of the men from the different periods, along with the fact that cognitive complexity seems to be the same on both graphs. Cognitive fluidity improves from mousterian to magdalenian suggesting that cognitive mechanisms such as sense sliding and analogies could be easier at the magdalenian level. Could we interpret this result as a due to a greater creativity at the magdalenian level than at the mousterian one? Further investigations are needed to state this, as well as enhanced data volume, potentially allowed by this entirely new method.     

Structures de la cabuamine et de la vincorine

Cabuamine is identified as O-methyl-hydrogeno akuammine.     

Contribution a l'etude de l'accumulation et de la toxicite de l'etain et du plomb chez des crustaces gammaridet

Résumé Nous avons étudiés les effets toxiques de l'accumulation de l'étain et du plomb sur les G. pulex d'eau douce et les G. locusta (Crustacés: Amphipodes) marin.Les expériences ont été faites dans des solutions de métaux d'eau douce et d'eau marine. Les concentrations de métal utilisées sont de 10 ppm, de 1 ppm et de 0.1 ppm. Les résultats nous ont montrés que les solutions de plomb sont plus toxique que les solutions de l'étain et les G. locusta sont plus sensibles que les G. pulex.Les valeurs de l'accumulation de métal ont été determinées par spectrographie des rayons X. Pour les deux espèces, une grande accumulation d'étain a été rencontrée dans le système digestif, la cuticule et l'hemolymphe et une accumulation de plomb a été rencontré dans le système digestif et la cuticule.

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The effects of tin (SnCl₄.5H₂O) and lead [Pb(NO₃)₂] on Gammarus pulex (L.) and Gammarus locusta (L.) have been studied. Three differents solutions (10 ppm, 1 ppm, 0.1 ppm) were applied for two metals. Lead was found to be more toxic than tin. The residues of metals in the organes and tissues of two species were determined by X ray spectrophotometry.

     

Évolution des caractères technologiques et typologiques des industries lithiques dans la stratigraphie de la Caune de l'Arago

The thick Quaternary deposits of the Caune de l’Arago (Pyrénées-Orientales, France) are dated to between 690 000 and 90 000 years old. At least fifteen different archeostratigraphical units have been identified within these deposits, each corresponding to distinct prehistoric occupations. Numerous stone tools made from several different rock types, have been discovered in each unit. The tools present specific characteristics concerning the choice of raw materials, the typology, and the technology used to produce them. Morpho-technological study of the different components of the assemblage contributes to a better understanding of the debitage methods used for their production. Each raw material is considered individually in order to ascertain its origin in the environment, its typological role and the technology applied during its exploitation. Defining production systems leads to the characterisation of the assemblages from each unit. When compared, they reveal common elements, as well as differences, suggesting evolutionary trends. Some observations are also made concerning the extent to which changing uses of the site may have influenced the general morphology of each assemblage, therefore taking into account exterior factors. Analysis of this rich stone tool assemblage helps to situate the Caune de l’Arago industry within the larger evolutionary context of the Lower Paleolithic in Mediterranean Europe.     

Action de la kinétine sur la croissance et la teneur en chlorophylles des racines

Lens roots form chlorophylls in well-developed chloroplasts when they are cultivated in continuous light. Chlorophyll accumulation was increased when kinetin (10^?4M) was added for a short time (24 h) of treatment. For a long time (72 h), the increase of chlorophyll content was reduced when roots were cultivated in light and with kinetin. When the roots were transferred from light to dark, chlorophyll content was decreased. This reduction was inhibited when roots were treated with kintin. From these present result it was supposed that kinetin acts on the catabolism and the anabolism of chlorophyll. The necessity of kinetin for chloroplast from amyloplast maturation and differentiation was discussed.     

Influence de l'intensité et de la longueur d'onde de la lumière sur le rendement des radicaux libres dans les semences de tomate et de carotte

Influence of light intensity and wavelength on the yield of free radicals in seeds of tomato and carrot.
Seeds of tomato ( Lycopersicum esculentum L. cv. Gribovsky-1180) and carrot ( Daucus carota L. cv. Santanet) were irradiated by continuous light of different wavelengths (white, blue, green, red, far-red and He-Ne laser) and different power density. Free radical output was measured using Electron Spin Resonance spectra (ESR). The dependence of the content of free radicals (FR) on the light power density was established. The yield of FR in the seeds irradiated with monochromatic light of the same power density was inversely proportional to the wavelength. The ESR spectra showed maximum absolute number of FR for white light. Successive irradiations gave cumulative effects on the output of free radicals in both directions: increase by the action of white light and decrease by the action of red and far-red light. The contact of irradiated seeds with steam decreased the amount of FR.