Effects of the transmethylation inhibitor S-adenosyl-homocysteine and of the methyl donor S-adenosyl-methionine on rat Leydig cell function in vitro

In purified rat Leydig cells, the methyl donor S-adenosyl-methionine (SAM), increases significantly in a dose dependent manner the [125I]hCG binding as well as the productions of cAMP and of testosterone; the competitive inhibitor of methylations S-adenosyl-homocysteine (SAH), has an opposite effect. Associated to oLH, SAM further enhances the cAMP synthesis while SAH inhibits significantly the adenylate cyclase activity. With regard to testosterone synthesis, SAM potentiates the stimulating roles of oLH and dbcAMP (27 and 38% increases, respectively) although SAH diminishes testosterone productions (48 and 35%, respectively under oLH and dbcAMP stimulations). Scatchard analysis has shown that SAM (1.4 mM) increases the number of LH/hCG binding sites on Leydig cells while SAH (1.4 mM) decreases it; LH/hCG Ka values are not modified neither by SAM nor by SAH. These data suggest that the in vitro regulation of steroidogenesis in purified rat Leydig cells may involve methylation processes (presumably phospholipids are the potential substrates of these reactions) which modulates the transmission of the hormonal signal through the membrane and affects the testosterone synthesis at a step beyond the adenylate cyclase.     

Demonstration of LH inhibitor(s) in sheep and human sera

In mature rat Leydig cells, the testosterone output (24 ng/10(6) Leydig cells/4hrs.) is increased 10 fold by LH; the addition of serum from either control or castrated or hypophysectomized rams inhibits (60%) the LH-stimulated testosterone production. Similarly, the incubation of immature rat Leydig cells with sera from hypophysectomized patients leads to a diminution (70 and 30% respectively) of both basal (0.98 ng) and LH stimulated (3.44 ng) testosterone biosynthesis. These data suggest the existence of an LH inhibitor (or inhibitors) in blood from ram and human; in addition, this substance is not only of testicular origin and is not an LH-related molecule.     

Desulfovibrio longus sp. nov., a sulfate-reducing bacterium isolated from an oil-producing well.

A novel type of sulfate-reducing bacteria with unusual morphology was isolated from an oil-producing well in the Paris Basin. The cells of this bacterium, strain SEBR 2582T (T = type strain), are long, thin, flexible rods, contain desulfoviridin, and are physiologically similar to members of the genus Desulfovibrio. On the basis of 16S rRNA sequence data, this strain should be included in the genus Desulfovibrio. However, strain SEBR 2582T differs from other members of this genus morphologically, physiologically, and phylogenetically. Thus, a new species, Desulfovibrio longus sp. nov., is proposed for this organism.     

Age-related changes in the function of the pituitary-gonadal axis in a sterile male rat mutant (hd/hd)

Testicular growth is depressed in the genetically sterile male rat (hd/hd) relative to its LE phenotype littermates (by 50% and 73% at 27 and 90 days of age, respectively). Within the hd/hd testis, both the tubular and seminiferous tubule tissues are affected by the mutation. In addition, there is significantly less germ cell production from the primary spermatocyte stage of spermatogenesis onwards and the total number of Sertoli cells observed is less. In the intertubular tissue, the total volume and the total number of Leydig cells per testis is significantly less, but the mean volume of an average Leydig cell is not modified. The serum gonadotropin levels are higher in the hd/hd rat, whereas from 40 days of age onwards the level of testosterone is lower. The FSH and LH binding affinity constants are unchanged by the mutation; however, the total number of FSH binding sites per 10(6) Sertoli cells is lower while that of LH per 10(6) Leydig cells is greater. Indeed, it is likely that the lesser concentration of serum testosterone in the hd/hd rat is a result of a smaller number of Leydig cells since their individual function is not modified. The testicular androgen binding protein (ABP) content and the ABP output towards the epididymis are lower as a consequence of both a lesser number and an altered function of the Sertoli cells.(ABSTRACT TRUNCATED AT 250 WORDS)     

Dissection of DNA Damage Responses Using Multiconditional Genetic Interaction Maps

1. Download : Download high-res image (256KB)
2. Download : Download full-size image

Highlights? A resource of genetic modules and networks induced by distinct types of DNA damage ? Networks distinguish DNA damage response pathways with high statistical power ? Rtt109, a histone acetyltransferase, affects the mutagenic bypass of DNA lesions ? The neddylation machinery and Irc21 affect cell-cycle control and genome stability     

The relative effects of local management and landscape context on weed seed predation and carabid functional groups

Farmland biodiversity and its associated ecosystem services are affected by agricultural activities at multiple spatial scales. Among these services, the regulation of weeds by invertebrate seed predators has received much attention recently but little is known about the relative effect of local management and landscape context of fields on this process. We monitored seed predation on four common weed species and carabid communities in 28 winter-cereals fields during five consecutive weeks in spring 2010. These fields were situated in contrasted landscape contexts and varied in terms of intensity of pesticide treatments and soil tillage regimes. Weed seed predation was strongly and positively related to the Shannon diversity of (strictly) granivorous carabids and to the activity–density of omnivorous carabids but negatively to the richness of omnivorous carabids. Weed seed predation and granivore diversity were positively related to landscape diversity and the proportion cover of temporary grassland within a 1000 m radius around focal fields and were negatively affected by the intensity of local pesticide treatments. No-till systems sheltered higher diversity of granivorous carabids but did not show higher seed predation rates. We showed that landscape composition factors had a higher relative influence than local practices factors on weed seed predation service. Consequently, weed management strategies should not only consider the management of single fields but also the surrounding landscape to preserve carabid biodiversity and enhance weed seed predation service.     

Biotic and Abiotic Soil Properties Influence Survival of Listeria monocytogenes in Soil

Listeria monocytogenes is a food-borne pathogen responsible for the potentially fatal disease listeriosis and terrestrial ecosystems have been hypothesized to be its natural reservoir. Therefore, identifying the key edaphic factors that influence its survival in soil is critical. We measured the survival of L. monocytogenes in a set of 100 soil samples belonging to the French Soil Quality Monitoring Network. This soil collection is meant to be representative of the pedology and land use of the whole French territory. The population of L. monocytogenes in inoculated microcosms was enumerated by plate count after 7, 14 and 84 days of incubation. Analysis of survival profiles showed that L. monocytogenes was able to survive up to 84 days in 71% of the soils tested, in the other soils (29%) only a short-term survival (up to 7 to 14 days) was observed. Using variance partitioning techniques, we showed that about 65% of the short-term survival ratio of L. monocytogenes in soils was explained by the soil chemical properties, amongst which the basic cation saturation ratio seems to be the main driver. On the other hand, while explaining a lower amount of survival ratio variance (11%), soil texture and especially clay content was the main driver of long-term survival of L. monocytogenes in soils. In order to assess the effect of the endogenous soils microbiota on L. monocytogenes survival, sterilized versus non-sterilized soils microcosms were compared in a subset of 9 soils. We found that the endogenous soil microbiota could limit L. monocytogenes survival especially when soil pH was greater than 7, whereas in acidic soils, survival ratios in sterilized and unsterilized microcosms were not statistically different. These results point out the critical role played by both the endogenous microbiota and the soil physic-chemical properties in determining the survival of L. monocytogenes in soils.     

Chemical preservation of tail feathers from Anchiornis huxleyi,a theropod dinosaur from the Tiaojishan Formation (Upper Jurassic,China)

A panel of geochemical techniques is used here to investigate the taphonomy of fossil feathers preserved in association with the skeleton of the Jurassic theropod Anchiornis huxleyi. Extant feathers were analysed in parallel to test whether the soft tissues morphologically preserved in the fossil also exhibit a high degree of chemical preservation. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) indicate that clays and iron oxide pseudomorphs occur in the surrounding sediment and also reveal the preservation of melanosome-like microbodies in the fossil. Carbon gradient along a depth profile and co-occurrence of carbon and sulphur are shown in the fossil by elastic backscattering (EBS) and particle-induced x-ray emission (PIXE), which are promising techniques for the elemental analysis of fossil soft tissues. The molecular composition of modern and fossil soft tissues was assessed from micro-attenuated total reflectance fourier transform infrared spectroscopy (micro-ATR FTIR), solid-state ¹³C nuclear magnetic resonance (CP-MAS ¹³C NMR) and pyrolysis gas chromatography mass spectrometry in the presence of TMAH (TMAH-Py-GC-MS). Results indicate that the proteinaceous material that comprises the modern feathers is not present in the fossil feathers. The fossil feathers and the embedding sediment exhibit a highly aliphatic character. However, substantial differences exist between these samples, revealing that the organic matter of the fossil feathers is, at least partially, derived from original constituents of the feathers. Our results suggest that, despite the morphological preservation of Anchiornis feathers, original proteins, that is keratin, were probably not preserved in the 160-myr-old feathers.