On the molecular mechanism of action of the tetracyclines

Résumé L'usage de modèles moléculaires CPK permet de comparer la structure des molécules de la tétracycline à celle des molécules du RNA. Il est suggéré que le site récepteur de la tétracycline sur le ribosome comprend soit du RNA à double tresse, dont les radicaux formés par GC/GC ou GC/AU, soit un complexe RNA/protéine stéréochimiquement analogue au précedent ou à la portion CC (ou CU) du RNA. Il peut enfin être remplacé par une portion isomorphique de protéine ayant une séquence aminoacidique telle que Glu-x-Glu (ou Glu-x-Gln).     

Enzymatic 5-hydroxylation of 3-methoxytyramine

Résumé Les homogénats de foie de rat et de foie de lapin contiennent un systéme enzymatique capable d'hydroxyler en position 5 la 4-hydroxy-3-méthoxy-phénéthylamine. Ce type d'oxydation pourrait représenter une voie biologique pour la transformation de catécholamines en substances analogues à la mescaline.

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This investigation was supported by PHS research Grant No. MH-11588 from the National Institute of Mental Health, Public Health Service, USA.     

In vitro incorporation of14C labeled precursors into swine coronary arterial phospholipids

Zusammenfassung Der Grad des Einbaus von¹⁴C-markierten Prekursoren in die Arterienphospholipide des Schweins war folgender: Cholin>Aethanolin>Serin> Glycerin>Format>Azetat. Bei Bebrütung von Arterien mit¹⁴C-Cholin oder¹⁴C-Aethanolamin trat ein deutlich erhöhter Einbau von¹⁴C in das Phosphatidylcholin auf.

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This investigation was supported by Grant No. 5R01-HE10172-03 from the National Heart Institute, U.S.P.H.S.     

Activation de l'adénylate cyclase et ses répercussions sur le taux intracellulaire d'AMP cyclique dans les cellules KB infectées produisant du virus Sendaï, infectieux sous l'influence de la trypsine

Summary KB cells infected by Sendaï virus can produce infectious virus if they are trypsinated twice over 24 h. Adenylate cyclase activity in infected KB cells is higher and more strongly activated by trypsin than that of control cells, but intracellular concentration of cAMP is the same, except during a short time after trypsinations, especially after the second trypsination which causes infectious virus production. During this short time, intracellular cAMP is slightly higher in infected cells. This miseffect of adenylate cyclase activation on intracellular cAMP concentrations might be related to an increased cell permeability caused by trypsin.     

DNA sequence and analysis of human chromosome 18

Chromosome 18 appears to have the lowest gene density of any human chromosome and is one of only three chromosomes for which trisomic individuals survive to term. There are also a number of genetic disorders stemming from chromosome 18 trisomy and aneuploidy. Here we report the finished sequence and gene annotation of human chromosome 18, which will allow a better understanding of the normal and disease biology of this chromosome. Despite the low density of protein-coding genes on chromosome 18, we find that the proportion of non-protein-coding sequences evolutionarily conserved among mammals is close to the genome-wide average. Extending this analysis to the entire human genome, we find that the density of conserved non-protein-coding sequences is largely uncorrelated with gene density. This has important implications for the nature and roles of non-protein-coding sequence elements.     

The DNA double-strand “breakome” of mouse spermatids

De novo germline mutations arise preferentially in male owing to fundamental differences between spermatogenesis and oogenesis. Post-meiotic chromatin remodeling in spermatids results in the elimination of most of the nucleosomal supercoiling and is characterized by transient DNA fragmentation. Using three alternative methods, DNA from sorted populations of mouse spermatids was used to confirm that double-strand breaks (DSB) are created in elongating spermatids and repaired at later steps. Specific capture of DSB was used for whole-genome mapping of DSB hotspots (breakome) for each population of differentiating spermatids. Hotspots are observed preferentially within introns and repeated sequences hence are more prevalent in the Y chromosome. When hotspots arise within genes, those involved in neurodevelopmental pathways become preferentially targeted reaching a high level of significance. Given the non-templated DNA repair in haploid spermatids, transient DSBs formation may, therefore, represent an important component of the male mutation bias and the etiology of neurological disorders, adding to the genetic variation provided by meiosis.     

真正“懂”啤酒的果蝇

啤酒的特殊气味我们轻易就能识别,对啤酒迷而言它的魅力更是不可抗拒。然而,科学家们最近发现,这种香味原本并不是为了吸引人类的,它的真正目的其实是为了吸引另一种生物——果蝇。事实证明,那些让人讨厌还总也抓不着的小苍蝇,对啤酒制造商来说并不仅仅是个大麻烦。一项新研究表明,在这种味道上,酵母和果蝇演化出了一种互惠互利的关系。酵母能够产生少量的挥发性物质,这些物质赋予了啤酒类似成熟水果的刺激性气味。