Zur Feinstruktur der Cricokaryozyten

Zusammenfassung Die in den Milchflecken des Mäusemesenterium als Folge von Speicherungsversuchen mit Trypanblau auftretenden Gewebeleukozyten (Cricokaryocyten) zeigen keine grundsätzlichen Unterschiede gegenüber den im Knochenmark und im strömenden Blut anzutreffenden ringkernigen myeloischen Zellen.     

Methods to measure the cutaneous transfer of radionuclides across the intact or lesioned epidermis,application to radiotoxicology

Although skin contamination by radionuclides is the most common cause of nuclear workers accidents, few studies dealing with the penetration of radioactive contamination through the skin are available. This work is a review of experimental methods that allow to assess transfer of radionuclides through the skin in occupational conditions, with or without skin trauma. The first section describes the different methods applied for skin transfer assessment of chemicals used in pharmacology. Major radionuclide contamination accidents can be associated with skin traumas. Thus, the second section describes the adaptation of these methods to radiotoxicology. Finally, the third section is an in vivo investigation of cobalt transfer (57CoCl2) through undamaged and damaged skin which simulates different industrial accident conditions (excoriation, acid or alcalin burn, scalding, branding).     

Operant conditioning of scratching in lemurs

An adult femaleLemur catta and an adult femaleEulemur fulvus were given edible rewards for scratching. Both subjects learned to scratch in order to obtain the rewards, showed diminished rates of scratching during periods of extinction, and learned to scratch preferentially with one foot when required. TheLemur catta subject was more responsive to the changing experimental conditions than theEulemur fulvus. The conditionability of scratching in primates does not appear to be directly related to the widespread occurrence of scratching in simian social contexts.     

Translational repression of MCL-1 couples stress-induced eIF2 alpha phosphorylation to mitochondrial apoptosis initiation

The integrated stress response (ISR) integrates a broad range of environmental and endogenous stress signals to the phosphorylation of the alpha-subunit of eukaryotic translation initiation factor 2 (eIF2 alpha). Although intense or prolonged activation of this pathway is known to induce apoptosis, the molecular mechanisms coupling stress-induced eIF2 alpha phosphorylation to the cell death machinery have remained incompletely understood. In this study, we characterized apoptosis initiation in response to classical activators of the ISR (tunicamycin, UVC, elevated osmotic pressure, arsenite). We found that all applied stress stimuli activated a mitochondrial pathway of apoptosis initiation. Rapid and selective down-regulation of the anti-apoptotic BCL-2 family protein MCL-1 preceded the activation of BAX, BAK, and caspases. Stabilization of MCL-1 blocked apoptosis initiation, while cells with reduced MCL-1 protein content were strongly sensitized to stress-induced apoptosis. Stress-induced elimination of MCL-1 occurred with unchanged protein turnover and independently of MCL-1 mRNA levels. In contrast, stress-induced phosphorylation of eIF2 alpha at Ser(51) was both essential and sufficient for the down-regulation of MCL-1 protein in stressed cells. These findings indicate that stress-induced phosphorylation of eIF2 alpha is directly coupled to mitochondrial apoptosis regulation via translational repression of MCL-1. Down-regulation of MCL-1 enables but not enforces apoptosis initiation in stressed cells.     

Chemical identification of<Emphasis Type="Italic"> N</Emphasis>-acyl homoserine lactone quorum-sensing signals produced by<Emphasis Type="Italic"> Sinorhizobium meliloti</Emphasis> strains in defined medium

The N-acyl homoserine lactone (AHL) quorum-sensing signals produced by Sinorhizobium meliloti strains AK631 and 1021 when cultured in a defined glucose-nitrate medium were identified by gas chromatography/mass spectrometry (GC/MS) and electrospray ionization tandem mass spectrometry (ESI MS/MS). Both strains synthesized several long-chain AHLs. Defined medium cultures of strain AK631 synthesized a complex mixture of AHLs with short acyl side chains. Strain 1021 produced no short-chain AHLs when grown on defined medium and made a somewhat different set of long-chain AHLs than previously reported for cultures in rich medium. While the two strains produced several AHLs in common, the differences in AHLs produced suggest that there may be significant differences in their patterns of quorum-sensing regulation.     

Evolution of lipid abundance and molecular composition during the podzolisation of laterites in the upper Amazon basin

In the upper Amazon basin, podzolisation involves the remobilization of large amounts of organic matter and chemical elements (Fe, Al, Si) previously accumulated in lateritic formations. In order to better understand the fate of organic matter in podzolic environments in this area, the evolution of lipid abundance and molecular composition were studied along a representative soil sequence showing the transition between a latosol and a well-developed podzol. Total solvent extracts were obtained from eight key soil samples from three profiles and their overlying litters, and enable us to follow both lateral and vertical evolutions. Lipid composition was determined by gas chromatography-mass spectrometry (GC-MS). Major compound classes include alkanes, alkanones, alkanols, alkanoic acids, ω-hydroxyacids, as well as aromatics, steroids and triterpenoids. Free lipids do not accumulate in the early stages of podzolisation but are abundant in well-developed podzolic horizons, possibly due to (i) combined acidity and waterlogging, (ii) limited amounts of complexing elements, (iii) a decreased microbial activity. The evolution of lipid composition is consistent with podzolisation mechanisms previously highlighted in the sequence. This paper provides further evidence for the occurrence of anoxic conditions in deep waterlogged podzolic horizons. It also shows that aromatic, phytotoxic compounds are stabilized in the well-developed podzol. This may play a role in the vegetation changes associated with podzolisation in the area.