Sphingolipid levels crucially modulate lateral microdomain organization of plasma membrane in living yeast

We report sphingolipid-related reorganization of gel-like microdomains in the plasma membrane of living Saccharomyces cerevisiae using trans-Parinaric acid (t-PnA) and 1,6-diphenyl-1,3,5-hexatriene (DPH). Compared to control, the gel-like domains were significantly reduced in the membrane of a sphingolipid-deficient lcb1-100 mutant. The same reduction resulted from sphingolipid depletion by myriocin. The phenotype could be reverted when a myriocin-induced block in sphingolipid biosynthesis was bypassed by exogenous dihydrosphingosine. Lipid order of less-ordered membrane regions decreased with sphingolipid depletion as well, as documented by DPH fluorescence anisotropy. The data indicate that organization of lateral microdomains is an essential physiological role of these structural lipids.     

Nitrogen fixation rates in algal turf communities of a degraded versus less degraded coral reef

Algal turf communities are ubiquitous on coral reefs in the Caribbean and are often dominated by N₂-fixing cyanobacteria. However, it is largely unknown (1) how much N₂ is actually fixed by turf communities and (2) which factors affect their N₂ fixation rates. Therefore, we compared N₂ fixation activity by turf communities at different depths and during day and night-time on a degraded versus a less degraded coral reef site on the island of Curaçao. N₂ fixation rates measured with the acetylene reduction assay were slightly higher in shallow (5–10-m depth) than in deep turf communities (30-m depth), and N₂ fixation rates during the daytime significantly exceeded those during the night. N₂ fixation rates by the turf communities did not differ between the degraded and less degraded reef. Both our study and a literature survey of earlier studies indicated that turf communities tend to have lower N₂ fixation rates than cyanobacterial mats. However, at least in our study area, turf communities were more abundant than cyanobacterial mats. Our results therefore suggest that turf communities play an important role in the nitrogen cycle of coral reefs. N₂ fixation by turfs may contribute to an undesirable positive feedback that promotes the proliferation of algal turf communities while accelerating coral reef degradation.     

Influence of Plant Root Exudates on the Mobility of Fuel Volatile Compounds in Contaminated Soils

Vegetation and its associated microorganisms play an important role in the behaviour of soil contaminants. One of the most important elements is root exudation, since it can affect the mobility, and therefore, the bioavailability of soil contaminants. In this study, we evaluated the influence of root exudates on the mobility of fuel derived compounds in contaminated soils. Samples of humic acid, montmorillonite, and an A horizon from an alumi-umbric Cambisol were contaminated with volatile contaminants present in fuel: oxygenates (MTBE and ETBE) and monoaromatic compounds (benzene, toluene, ethylbenzene and xylene). Natural root exudates obtained from Holcus lanatus and Cytisus striatus and ten artificial exudates (components frequently found in natural exudates) were added to the samples, individually and as a mixture, to evaluate their effects on contaminant mobility. Fuel compounds were analyzed by headspace-gas chromatography-mass spectrometry. In general, the addition of natural and artificial exudates increased the mobility of all contaminants in humic acid. In A horizon and montmorillonite, natural or artificial exudates (as a mixture) decreased the contaminant mobility. However, artificial exudates individually had different effects: carboxylic components increased and phenolic components decreased the contaminant mobility. These results established a base for developing and improving phytoremediation processes of fuel-contaminated soils.     

Androgen receptor heterogeneity in LNCaP cells is caused by a hormone independent phosphorylation step

Androgen receptor synthesis and modification were studied in the human LNCaP cell line. Immunoblotting showed that the androgen receptor migrated as a closely spaced 110–112 kDa doublet on SDS-PAGE gels. Most of the receptor protein is present in the higher molecular mass form. Labelling experiments with [³⁵S]methionine showed that the androgen receptor is synthesized as a single 110 kDa protein which is rapidly converted to a 112 kDa protein. Upon alkaline phosphatase treatment a gradual elimination of the 112 kDa isoform with a concomitant increase of the 110 kDa isoform was seen, indicating that the observed 110 to 112 kDa upshift reflects androgen receptor phosphorylation. Furthermore, it is shown that both isoforms can bind hormone and undergo a hormone dependent transformation to a tight nuclear binding form, indicating that the 110 to 112 kDa conversion is not an obligatory step for hormone binding or receptor transformation.     

Maintenance of Leukemia-Initiating Cells Is Regulated by the CDK Inhibitor Inca1

Functional differences between healthy progenitor and cancer initiating cells may provide unique opportunities for targeted therapy approaches. Hematopoietic stem cells are tightly controlled by a network of CDK inhibitors that govern proliferation and prevent stem cell exhaustion. Loss of Inca1 led to an increased number of short-term hematopoietic stem cells in older mice, but Inca1 seems largely dispensable for normal hematopoiesis. On the other hand, Inca1-deficiency enhanced cell cycling upon cytotoxic stress and accelerated bone marrow exhaustion. Moreover, AML1-ETO9a-induced proliferation was not sustained in Inca1-deficient cells in vivo. As a consequence, leukemia induction and leukemia maintenance were severely impaired in Inca1^−/− bone marrow cells. The re-initiation of leukemia was also significantly inhibited in absence of Inca1^−/− in MLL—AF9- and c-myc/BCL2-positive leukemia mouse models. These findings indicate distinct functional properties of Inca1 in normal hematopoietic cells compared to leukemia initiating cells. Such functional differences might be used to design specific therapy approaches in leukemia.     

Expression of human aldo-keto reductase 1C2 in cell lines of peritoneal endometriosis: potential implications in metabolism of progesterone and dydrogesterone and inhibition by progestins

The human aldo-keto reductase AKR1C2 converts 5α-dihydrotestosterone to the less active 3α-androstanediol and has a minor 20-ketosteroid reductase activity that metabolises progesterone to 20α-hydroxyprogesterone. AKR1C2 is expressed in different peripheral tissues, but its role in uterine diseases like endometriosis has not been studied in detail. Some progestins used for treatment of endometriosis inhibit AKR1C1 and AKR1C3, with unknown effects on AKR1C2. In this study we investigated expression of AKR1C2 in the model cell lines of peritoneal endometriosis, and examined the ability of recombinant AKR1C2 to metabolise progesterone and progestin dydrogesterone, as well as its potential inhibition by progestins. AKR1C2 is expressed in epithelial and stromal endometriotic cell lines at the mRNA level. The recombinant enzyme catalyses reduction of progesterone to 20α-hydroxyprogesterone with a 10-fold lower catalytic efficiency than the major 20-ketosteroid reductase, AKR1C1. AKR1C2 also metabolises progestin dydrogesterone to its 20α-dihydrodydrogesterone, with 8.6-fold higher catalytic efficiency than 5α-dihydrotestosterone. Among the progestins that are currently used for treatment of endometriosis, dydrogesterone, medroxyprogesterone acetate and 20α-dihydrodydrogesterone act as AKR1C2 inhibitors with low μM K(i) values in vitro. Their potential in vivo effects should be further studied.     

In Vivo Volatile Organic Compound Signatures of Mycobacterium avium subsp. paratuberculosis

Mycobacterium avium ssp. paratuberculosis (MAP) is the causative agent of a chronic enteric disease of ruminants. Available diagnostic tests are complex and slow. In vitro, volatile organic compound (VOC) patterns emitted from MAP cultures mirrored bacterial growth and enabled distinction of different strains. This study was intended to determine VOCs in vivo in the controlled setting of an animal model. VOCs were pre-concentrated from breath and feces of 42 goats (16 controls and 26 MAP-inoculated animals) by means of needle trap microextraction (breath) and solid phase microextraction (feces) and analyzed by gas chromatography/ mass spectrometry. Analyses were performed 18, 29, 33, 41 and 48 weeks after inoculation. MAP-specific antibodies and MAP-specific interferon-γ-response were determined from blood. Identities of all marker-VOCs were confirmed through analysis of pure reference substances. Based on detection limits in the high pptV and linear ranges of two orders of magnitude more than 100 VOCs could be detected in breath and in headspace over feces. Twenty eight substances differed between inoculated and non-inoculated animals. Although patterns of most prominent substances such as furans, oxygenated substances and hydrocarbons changed in the course of infection, differences between inoculated and non-inoculated animals remained detectable at any time for 16 substances in feces and 3 VOCs in breath. Differences of VOC concentrations over feces reflected presence of MAP bacteria. Differences in VOC profiles from breath were linked to the host response in terms of interferon-γ-response. In a perspective in vivo analysis of VOCs may help to overcome limitations of established tests.     

Testosterone and its effects on courtship in golden-collared manakins (Manacus vitellinus): seasonal, sex, and age differences

Male golden-collared manakins gather on leks and perform an acrobatic display to attract females. In temperate breeding species, testosterone (T) activation of courtship displays has been well studied. Few studies have examined T activation of displays in tropical species; even fewer have explored the activational role of T in elaborate courtship displays such as in the manakin. In some tropical species, including manakins, territorial aggression or song behavior are uncoupled from T. We have previously shown that T activates display behavior in manakin males when endogenous T levels are low in the non-courtship season. To understand how T functions in breeding birds, we examined T levels in a large group of manakins sampled during the courtship and non-courtship season. In addition, during the courtship season, we gave T implants to adult males, juvenile males, and females. We found that T levels were low during the non-courtship season and comparatively higher on average during the courtship season. However, T levels were low in many adult males during the courtship season, especially when compared to temperate breeding species. Regardless of initial endogenous T levels during the courtship season, T implants did not increase the display frequency of adult males. T-treated females and juvenile males did display under similar conditions. Our data suggest that the effects of T on manakin display vary with season, sex, and age and that high T is not necessary for display.