Induction of control genes in intestinal gluconeogenesis is sequential during fasting and maximal in diabetes

We studied in rats the expression of genes involved in gluconeogenesis from glutamine and glycerol in the small intestine (SI) during fasting and diabetes. From Northern blot and enzymatic studies, we report that only phosphoenolpyruvate carboxykinase (PEPCK) activity is induced at 24 h of fasting, whereas glucose-6-phosphatase (G-6-Pase) activity is induced only from 48 h. Both genes then plateau, whereas glutaminase and glycerokinase strikingly rebound between 48 and 72 h. The two latter genes are fully expressed in streptozotocin-diabetic rats. From arteriovenous balance and isotopic techniques, we show that the SI does not release glucose at 24 h of fasting and that SI gluconeogenesis contributes to 35% of total glucose production in 72-h-fasted rats. The new findings are that 1) the SI can quantitatively account for up to one-third of glucose production in prolonged fasting; 2) the induction of PEPCK is not sufficient by itself to trigger SI gluconeogenesis; 3) G-6-Pase likely plays a crucial role in this process; and 4) glutaminase and glycerokinase may play a key potentiating role in the latest times of fasting and in diabetes.     

From dormant to germinating spores of Streptomyces coelicolor A3(2): new perspectives from the crp null mutant

The complete understanding of the morphological differentiation of streptomycetes is an ambitious challenge as diverse sensors and pathways sensitive to various environmental stimuli control the process. Germination occupies a particular position in the life cycle as the good achievement of the process depends on events occurring both during the preceding sporulation and during germination per se. The cyclic AMP receptor protein (crp) null mutant of Streptomyces coelicolor, affected in both sporulation and germination, was therefore presented as a privileged candidate to highlight new proteins involved in the shift from dormant to germinating spores. Our multidisciplinary approach-combining in vivo data, the analysis of spores morphological properties, and a proteome study-has shown that Crp is a central regulatory protein of the life cycle in S. coelicolor; and has identified spores proteins with statistically significant increased or decreased expression that should be listed as priority targets for further investigations on proteins that trigger both ends of the life cycle.     

Synthesis and antiviral evaluation of thieno[3,4-d]pyrimidine C-nucleoside analogues of 2′,3′-dideoxy- and 2′,3′-dideoxy-2′,3′-didehydro-adenosine and -inosine

Several thieno[3,4-d]pyrimidine derivatives, including four hitherto unknown 2′,3′-dideoxy- and 2′,3′-dideoxy-2′,3′-didehydro-C-nucleoside analogues of adenosine and inosine have been synthesized. When evaluated in cell culture experiments against human immunodeficiency virus, none of the tested compounds exhibited any significant antiviral effect, while two of them showed some cytotoxicity.     

Minimal cut sets in biochemical reaction networks

MOTIVATION: Structural studies of metabolic networks yield deeper insight into topology, functionality and capabilities of the metabolisms of different organisms. Here, we address the analysis of potential failure modes in metabolic networks whose occurrence will render the network structurally incapable of performing certain functions. Such studies will help to identify crucial parts in the network structure and to find suitable targets for repressing undesired metabolic functions. RESULTS: We introduce the concept of minimal cut sets for biochemical networks. A minimal cut set (MCS) is a minimal (irreducible) set of reactions in the network whose inactivation will definitely lead to a failure in certain network functions. We present an algorithm which enables the computation of the MCSs in a given network related to user-defined objective reactions. This algorithm operates on elementary modes. A number of potential applications are outlined, including network verifications, phenotype predictions, assessing structural robustness and fragility, metabolic flux analysis and target identification in drug discovery. Applications are illustrated by the MCSs in the central metabolism of Escherichia coli for growth on different substrates. AVAILABILITY: Computation and analysis of MCSs is an additional feature of the FluxAnalyzer (freely available for academic users upon request, special contracts for industrial companies; see web page below). Supplementary information: http://www.mpi-magdeburg.mpg.de/projects/fluxanalyzer     

Quail Egg Yolk: A Novel Cryoprotectant for the Freeze Preservation of Poitou Jackass Sperm

For many years, attempts have been made to establish a sperm bank for the Poitou jackass population which is threatened with extinction. Unfortunately, no cryopreservation technique has ever been described for spermatozoa of this species. In an attempt to find a suitable technique, we studied the relative effectiveness of chicken egg yolk and quail egg yolk in preserving the motility and characteristics of movement of Poitou jackass spermatozoa during the freezing–thawing process. Semen was diluted to 60 × 10⁶sperm/ml in a preservation medium containing 4% (v/v) glycerol with 0, 2, 5, 10, 15, or 20% (v/v) of chicken or quail egg yolk. The chemical composition of these two eggs was compared. Effects were assessed using an automated analyzer which measured curvilinear velocity (VCL), straight line velocity (VSL), and the velocity of the average path. Linearity was defined as VSL/VCL × 100. The amplitude of the lateral head displacement was also measured. It was found that after the freeze–thaw process, quail egg yolk improved the percentages of motile and progressively undulating spermatozoa and the movement characteristics compared with chicken egg yolk. The optimal concentration of quail egg yolk was 10%. The general composition of the two types of egg yolk were similar, but quail egg yolk contained significantly more phosphatidylcholine, less phosphatidylethanolamine, and a smaller ratio of polyunsaturated to saturated fatty acids than chicken egg yolk. The improvement of motility for frozen–thawed Poitou jackass spermatozoa using frozen–thawed quail egg yolk compared to chicken egg yolk may be due to the differences in composition of the two yolks.     

Essential oil and terpenoids of Mikania micrantha

Twenty-seven mainly terpenoid constituents were identified in the essential oil of Mikania micrantha whole plant. Higher terpenoids present in the same plant included two kaurene derivatives and taraxasterol.     

Brain responses to violet, blue, and green monochromatic light exposures in humans: prominent role of blue light and the brainstem

Background

Relatively long duration retinal light exposure elicits nonvisual responses in humans, including modulation of alertness and cognition. These responses are thought to be mediated in part by melanopsin-expressing retinal ganglion cells which are more sensitive to blue light than violet or green light. The contribution of the melanopsin system and the brain mechanisms involved in the establishment of such responses to light remain to be established.

Methodology/Principal Findings

We exposed 15 participants to short duration (50 s) monochromatic violet (430 nm), blue (473 nm), and green (527 nm) light exposures of equal photon flux (10¹³ph/cm²/s) while they were performing a working memory task in fMRI. At light onset, blue light, as compared to green light, increased activity in the left hippocampus, left thalamus, and right amygdala. During the task, blue light, as compared to violet light, increased activity in the left middle frontal gyrus, left thalamus and a bilateral area of the brainstem consistent with activation of the locus coeruleus.

Conclusion/Significance

These results support a prominent contribution of melanopsin-expressing retinal ganglion cells to brain responses to light within the very first seconds of an exposure. The results also demonstrate the implication of the brainstem in mediating these responses in humans and speak for a broad involvement of light in the regulation of brain function.     

Reversible inactivation of the transcriptional function of P53 protein by farnesylation

Background  

The use of integrating viral vectors in Gene therapy clinical trials has pointed out the problem of the deleterous effect of the integration of the ectopic gene to the cellular genome and the safety of this strategy. We proposed here a way to induce the death of gene modified cells upon request by acting on a pro-apoptotic protein cellular localization and on the activation of its apoptotic function.     

Protein mutagenesis with monodispersity-based quality probing: selective inactivation of p53 degradation and DNA-binding properties of HPV E6 oncoprotein

Interpretation of protein mutagenesis experiments requires the ability to distinguish functionally relevant mutations from mutations affecting the structure. When a protein is expressed soluble in bacteria, properly folded mutants are expected to remain soluble whereas misfolded mutants should form insoluble aggregates. However, this rule may fail for proteins fused to highly soluble carrier proteins. In a previous study, we analysed the biophysical status of HPV oncoprotein E6 fused to the C-terminus of maltose-binding protein (MBP) and found that misfolded E6 moieties fused to MBP formed soluble aggregates of high molecular weight. By contrast, preparations of properly folded E6 fused to MBP were monodisperse. Here, we have used this finding to evaluate the quality of 19 MBP-fused E6 site-directed mutants by using a light scattering assay performed in a fluorimeter. This assay guided us to rule out structurally defective mutants and to obtain functionally relevant E6 mutants selectively altered for two molecular activities: degradation of tumour suppressor p53 and DNA recognition.     

2′-and/or 3Y-Deoxy-β-L-pentofuranosyl Nucleoside Derivatives: Stereospecific Synthesis and Antiviral Activities

Abstract

Several L-enantiomers of nucleoside analogues were stereospecifically synthesized by a multi-step reaction from L-xylose and their antiviral properties were examined in vitro. Two of them, namely β-L-2′,3,′-dideoxycytidine (β-L-ddC) and its 5-fluoro derivative (β-L-FddC) were found to have potent anti-human immunodeficiency virus (HIV) and significant anti-hepatitis B virus (HBV) activities in cell cultures.