Thermopreferendum de l'Araignée socialeAgelena consociata Denis

Résumé Le présent article a pour but d'analyser les multiples facteurs pouvant perturber l'étude duthermopreferendum de l'Araignée socialeAgelena consociata Denis et d'exposer les résultats obtenus.Pour satisfaire lethigmotactisme très développé de ces Araignées, la boîte servant à cette étude est cloisonnée et sa hauteur est de 1 cm.Un abreuvoir placé dans chaque compartiment maintient une humidité saturante pour compenser le gradient hygrométrique résultant du gradient thermique.L'expérience doit durer plusieurs jours et ne commencer que 24 heures après l'introduction des Araignées: premièrement, parce que cela permet aux Araignées de recouvrir le fond de la boîte d'une nappe de soie, ce qui contribue à les rapprocher de leurs conditions naturelles; deuxièmement, parce que la phase d'activité de ces Araignées est nocturne. Or, il semble que c'est lors de cette phase que les animaux choisissent leurthermopreferendum.Il ne faut pas effectuer plus de trois relevés par jour, sans quoi les Araignées, très sensibles aux perturbations, ont tendance à se diriger vers l'extrémité froide.Lethermopreferendum desAgelena consociata se situe à 22°65±0,10 pour la température de l'air et à 22°89±0,12 par rapport à la température du sol.

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Summary This article aims at analysing the various causes which can disturb the study of thethermopreferendum of social SpidersAgelena consociata Denis and aims at explaining the achieved results.In order to satisfy the extremely developedthigmotactisme of these Spiders, the box used for that study has been partitioned off; its height is 1 cm.A small piece of wet cotton-wool placed into each partition maintains a saturated humidity to compensate the hygrometric gradient resulting from the thermic gradient.The experiment must go on during several days and must only begin a day after having put the Spiders into the box: first because the Spiders can cover the bottom with a cobweb, which contributes to create almost natural conditions; secondly because the period of activity of these Spiders takes place at night. As a fact it seems that it is during this period that the Spiders choose theirthermopreferendum.More than three readings a day must not be performed because otherwise the Spiders, wich are very sensitive to disturbances, are inclined to go towards the cold end of the box.Thethermopreferendum of theAgelena consociata takes place at 22°65 C±0,10 C as for the temperature of the air and at 22°89 C±0,12 C as for the temperature of the ground.

     

Stereotactic system and apparatus for use with magnetic resonance imaging, computerized tomography, and digital subtraction imaging

A light-weight nonmagnetic, nonconductive instrument has been devised for use with magnetic resonance imaging, computerized tomography, and digital subtraction imaging for work in the field of epilepsy, brain tumors and vascular lesions. The apparatus' main characteristic is its ability to use optionally either the lateral orthogonal or the spherical-radial approach.     

Correlates and implications of breast-feeding practices in Bas Zaire

A sample of 1871 women having a child under 3 years old in Bas Zaire was studied to determine the correlates of breastfeeding practices and to examine the interrelationships among breastfeeding, contraceptive practices and desire for pregnancy. The methods of analysis applied were life table analysis and its multivariate extensions. Most of the findings in this analysis are consistent with current literature on the correlates of the duration of breastfeeding. Maternal education, economic status, age, parity, urban residence, pregnancy, and sex of the index child were significantly related to the length of breastfeeding. Among non-pregnant women, current desire for pregnancy was also related to breastfeeding status when the length of time since birth of the last child was taken into consideration. Rural women were reportedly ready for another pregnancy sooner after the birth of their last child than were urban women. Breastfeeding appears to be the most important means of contraceptive protection in the study population. The effective traditional method of extended postpartum abstinence is not widely prevalent, particularly among the urban sample, and indeed seems to be on the decline. The data presented here also suggest that breastfeeding pratices are changing in this area of Africa where little economic development has occurred in the past 20 years. This research suggests that if current trends continue, fertility levels are likely to increase significantly. The findings also indicate that Bas Zairian mothers want to space their births and for this reason may be receptive to family planning programs that use appropriate strategies.     

Insertion of a foreign nucleotide sequence into mitochondrial DNA causes senescence in Neurospora intermedia

The kalilo variants of Neurospora contain a cytoplasmic genetic factor that causes senescence. This factor is a 9.0 kb transposable element (kalDNA) that lacks nucleotide sequence homology with mtDNA and is inserted into the mitochondrial chromosome, often at sites located within the open reading frame in the intron-DNA of the mitochondrial 25S-rRNA gene. Genomes containing the "foreign" DNA insert accumulate during growth, and death occurs as the cells become deficient in functional large and small subunits of mitochondrial ribosomes. The kalDNA transposon may be an "activator" element that causes breaks in mtDNA. Nonsenescing [+] strains of Neurospora do not contain kalDNA.     

Evidence for only one iron-sulfur cluster in center X of photosystem I from higher plants

In the photosystem I of thylakoid membranes, the photoinduced electron transfer involves three iron-sulfur centers, A, B, and X. Among them, center X is characterized by very unusual spectroscopic and redox properties. Recent arguments have been presented in favor of a [2Fe-2S] structure for the clusters implicated in this center, but the number of these clusters is still a controversial question. By using an original EPR method, based on the differences in the relaxation properties of A, B, and X, we have determined the stoichiometry for the iron-sulfur clusters in photosystem I. Our measurements indicate that center X is composed of a single iron-sulfur cluster per P700. The possible implications of this result for the polypeptide composition of the core reaction center are discussed.     

Molecular cloning, functional expression and pharmacological characterization of a human bradykinin B2 receptor gene.

The gene encoding a putative G protein-coupled receptor (HG10) was cloned from human genomic DNA by low stringency PCR and found to be homologous to the recently described rat bradykinin B2 receptor. The receptor was expressed in xenopus oocytes and stably transfected CHO cell lines. Binding studies demonstrated that HG10 encodes a high affinity BK receptor with an apparent Kd of 150 pM. Displacement by BK agonists and antagonists allowed the characterization of the receptor as a B2 subtype. Functional coupling to the Ca(2+)-phosphatidylinositol cascade was demonstrated in transfected CHO cells where inositol phosphates accumulation and intracellular calcium concentration were elevated in response to BK stimulation. The agonistic and antagonistic properties of BK analogs do not match strictly the pharmacological profile described for the rat or guinea pig B2 receptor subtypes or the putative B3 subtype. This discrepancy is attributed either to species variability or to differences in the coupling efficiency of receptors to the transduction cascade in different cell types. From our results, the existence of B3 receptors and of B2 subtypes appears questionable.