Stimulation of in vitro mitochondrial protein synthesis by yeast cytoplasmic extracts is caused by guanyl nucleotides

Micromolar concentrations of GDP or GTP stimulate protein synthesis by isolated yeast mitochondria 3- to 10-fold even if alpha-ketoglutarate and an ATP-regenerating system are present. No stimulation is observed with GMP, UTP, CTP, TTP, and the nonhydrolyzable GTP analogues guanyl(beta, gamma-methylene) diphosphate and guanyl imidodiphosphate. This stimulatory effect of exogenously added guanyl nucleotides may answer the long standing question why protein synthesis by isolated mitochondria is so slow. It can also explain previous reports by two other laboratories that a high speed supernatant from yeast cells stimulates protein synthesis by isolated mitochondria. The supernatant contains nondialyzable GMP which is converted to GDP under the conditions used for assaying mitochondrial protein synthesis. The stimulatory effect of high speed supernatants is abolished by 5'-nucleotidase (which degrades GMP) or by trypsin (which destroys supernatant protein(s) necessary for converting GMP to GDP). No evidence was obtained that the stimulatory effect of high speed supernatants was caused by precursors to cytoplasmically made cytochrome c oxidase subunits.     

Mutations in putative intervening sequences of the mitochondrial cytochrome b gene of yeast produce abnormal cytochrome b polypeptides.

The apoprotein of yeast cytochrome b is translated on mitochondrial ribosomes and coded for by a split gene which is located in the COB-BOX region on mitochondrial DNA. With the aid of an antibody against cytochrome b, we identified the cytochrome b-cross-reacting polypeptides of respiration-deficient mutants mapping either in coding or intervening sequences of the cytochrome b gene. Most mutations in the coding regions caused the accumulation of a single apocytochrome b fragment whose apparent molecular weight (12,000 to 26,600) depended on the map position of the mutation. In contrast, mutations in putative intervening sequences often led to multiple new polypeptides immunologically related to apocytochrome b. Some of these abnormal polypeptides were considerably larger than wild type apocytochrome b. This suggests that mutations in intervening sequences can thus generate aberrant polypeptide products.     

RGD Surface Functionalization of the Hydrophilic Acrylic Intraocular Lens Material to Control Posterior Capsular Opacification

Posterior Capsular Opacification (PCO) is the capsule fibrosis developed on implanted IntraOcular Lens (IOL) by the de-differentiation of Lens Epithelial Cells (LECs) undergoing Epithelial Mesenchymal Transition (EMT). Literature has shown that the incidence of PCO is multifactorial including the patient''s age or disease, surgical technique, and IOL design and material. Reports comparing hydrophilic and hydrophobic acrylic IOLs have shown that the former has more severe PCO. On the other hand, we have previously demonstrated that the adhesion of LECs is favored on hydrophobic compared to hydrophilic materials. By combining these two facts and contemporary knowledge in PCO development via the EMT pathway, we propose a biomimetically inspired strategy to promote LEC adhesion without de-differentiation to reduce the risk of PCO development. By surface grafting of a cell adhesion molecule (RGD peptide) onto the conventional hydrophilic acrylic IOL material, the surface-functionalized IOL can be used to reconstitute a capsule-LEC-IOL sandwich structure, which has been considered to prevent PCO formation in literature. Our results show that the innovative biomaterial improves LEC adhesion, while also exhibiting similar optical (light transmittance, optical bench) and mechanical (haptic compression force, IOL injection force) properties compared to the starting material. In addition, compared to the hydrophobic IOL material, our bioactive biomaterial exhibits similar abilities in LEC adhesion, morphology maintenance, and EMT biomarker expression, which is the crucial pathway to induce PCO. The in vitro assays suggest that this biomaterial has the potential to reduce the risk factor of PCO development.     

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.     

The Amusic Brain: Lost in Music,but Not in Space

Congenital amusia is a neurogenetic disorder of music processing that is currently ascribed to a deficit in pitch processing. A recent study challenges this view and claims the disorder might arise as a consequence of a general spatial-processing deficit. Here, we assessed spatial processing abilities in two independent samples of individuals with congenital amusia by using line bisection tasks (Experiment 1) and a mental rotation task (Experiment 2). Both amusics and controls showed the classical spatial effects on bisection performance and on mental rotation performance, and amusics and controls did not differ from each other. These results indicate that the neurocognitive impairment of congenital amusia does not affect the processing of space.     

Import of an incompletely folded precursor protein into isolated mitochondria requires an energized inner membrane, but no added ATP.

We have studied the post-translational import of incomplete precursor chains into isolated yeast mitochondria. The precursor was a fusion protein containing a mitochondrial presequence attached to mouse dihydrofolate reductase. In vitro-synthesis of the precursor was interrupted by the elongation inhibitor cycloheximide and the arrested nascent chains cosedimenting with ribosomes were released by EDTA. These incomplete chains were efficiently imported by isolated yeast mitochondria; their import resembled that of the complete precursor in requiring an energized inner membrane and a mitochondrial presequence. It differed from that of the completed precursor in its resistance to methotrexate (which only binds to correctly folded dihydrofolate reductase) and its independence of added ATP. The incomplete chains were also more sensitive to proteinase K than the completed precursor. We conclude that the incomplete chains were incompletely folded and suggest that the lack of tight folding caused import into mitochondria to become independent of added ATP. This implies that ATP may participate, directly or indirectly, in the unfolding of the precursor for its transport into mitochondria.