Establishment of cellulolytic bacteria in the digestive tract of conventionally reared young mice: effect of the dietary cellulose content in the adult

Cellulolytic bacteria became established 12 days after birth in the caecum and colon of conventionally-reared mice fed a diet containing 5 p. 100 crude cellulose (Weende). Their population reached a level between 10(6) and 10(7) bacteria per gram of digestive contents in 25-day-old animals. However, variations between animals were very large; 20 to 50% of the individuals were free of cellulolytic bacteria. A low cellulolytic population was observed in adult mice fed a cellulose-free diet. The amount of cellulose in the diet and its nature (crude or pure cellulose) affected the number of cellulolytic bacteria: the higher the percentage of cellulose in the diet, the higher the number of cellulolytic bacteria, in particular with crude cellulose-containing diet.     

Evaluation of Antibacterial Activity of Lavandulapedunculata subsp. atlantica (Braun‐Blanq.) Romo Essential Oil and Selected Terpenoids against Resistant Bacteria Strains–Structure–Activity Relationships

The genus Lavandula is known for its different uses in traditional medicine. This study is interested in the chemical composition of Lavandulapedunculata subsp.atlantica (Braun‐Blanq. ) Romo as well as evaluating its antibacterial potential against multi‐resistant strains. The analysis of Lavandulaatlantica essential oil (LAEO) allows the identification of 47 components representing 93.6 % of all identified. The main constituent of LAEO was camphor (50.4 %), followed by fenchone (14.1 %) and camphene (5.6 %). The antibacterial assays revealed that LAEO was active against all the studied bacteria. A preliminary study of the relationship between certain terpenoids and antibacterial activity was also carried out in order to note the compound(s) that are responsible for LAEO's antibacterial activity. This study showed that the activity of the essential oil may be due to the presence of certain minor compounds such as carvone, considering the presence of the synergistic effect between the essential oil.     

Essential Oil Variability and Biological Activities of Tetraclinis articulata (Vahl) Mast. Wood According to the Extraction Time

In the present work, the hydrodistillation (HD) and microwave‐assisted hydrodistillation (MAHD) kinetics of essential oil (EO) extracted from Tetraclinis articulata (Vahl ) Mast. wood was conducted, in order to assess the impact of extraction time and technique on chemical composition and biological activities. Gas chromatography (GC) and GC/mass spectrometry analyses showed significant differences between the extracted EOs, where each family class or component presents a specific kinetic according to extraction time, technique and especially for the major components: camphene, linalool, cedrol, carvacrol and α‐acorenol. Furthermore, our findings showed a high variability for both antioxidant and anti‐inflammatory activities, where each activity has a specific effect according to extraction time and technique. The highlighted variability reflects the high impact of extraction time and technique on chemical composition and biological activities, which led to conclude that we should select EOs to be investigated carefully depending on extraction time and technique, in order to isolate the bioactive components or to have the best quality of EO in terms of biological activities and preventive effects in food.     

Biofertilizing Effect of Chlorella sorokiniana Suspensions on Wheat Growth

Journal of Plant Growth Regulation - The potential of microalgae as a biofertilizer in agriculture is increasingly recognized. We studied the effect of applications of Chlorella on growth of wheat...     

An essential role of s-adenosyl-L-methionine:L-methionine s-methyltransferase in selenium volatilization by plants. Methylation of selenomethionine to selenium-methyl-L-selenium- methionine,the precursor of volatile selenium

Selenium (Se) phytovolatilization, the process by which plants metabolize various inorganic or organic species of Se (e.g. selenate, selenite, and Se-methionine [Met]) into gaseous Se forms (e.g. dimethylselenide), is a potentially important means of removing Se from contaminated environments. Before attempting to genetically enhance the efficiency of Se phytovolatilization, it is essential to elucidate the enzymatic pathway involved and to identify its rate-limiting steps. The present research tested the hypothesis that S-adenosyl-L-Met:L-Met S-methyltransferase (MMT) is the enzyme responsible for the methylation of Se-Met to Se-methyl Se-Met (SeMM). To this end, we identified and characterized an Arabidopsis T-DNA mutant knockout for MMT. The lack of MMT in the Arabidopsis T-DNA mutant plant resulted in an almost complete loss in its capacity for Se volatilization. Using chemical complementation with SeMM, the presumed enzymatic product of MMT, we restored the capacity of the MMT mutant to produce volatile Se. Overexpressing MMT from Arabidopsis in Escherichia coli, which is not known to have MMT activity, produced up to 10 times more volatile Se than the untransformed strain when both were supplied with Se-Met. Thus, our results provide in vivo evidence that MMT is the key enzyme catalyzing the methylation of Se-Met to SeMM.     

Indirect activation of the epithelial Na+ channel by trypsin

We tested the hypothesis that the serine protease trypsin can indirectly activate the epithelial Na(+) channel (ENaC). Experiments were carried out in Xenopus oocytes and examined the effects on the channel formed by all three human ENaC subunits and that formed by Xenopus epsilon and human beta and gamma subunits (epsilonbetagammaENaC). Low levels of trypsin (1-10 ng/ml) were without effects on the oocyte endogenous conductances and were specifically used to test the effects on ENaC. Addition of 1 ng/ml trypsin for 60 min stimulated the amiloride-sensitive human ENaC conductance (g(Na)) by approximately 6-fold. This effect on the g(Na) was [Na(+)]-independent, thereby ruling out an interaction with channel feedback inhibition by Na(+). The indirect nature of this activation was confirmed in cell-attached patch clamp experiments with trypsin added to the outside of the pipette. Trypsin was comparatively ineffective at activating epsilonbetagammaENaC, a channel that exhibited a high spontaneous open probability. These observations, in combination with surface binding experiments, indicated that trypsin indirectly activated membrane-resident channels. Activation by trypsin was also dependent on catalytic activity of this protease but was not accompanied by channel subunit proteolysis. Channel activation was dependent on downstream activation of G-proteins and was blocked by G-protein inhibition by injection of guanyl-5'-yl thiophosphate and by pre-stimulation of phospholipase C. These data indicate a receptor-mediated activation of ENaC by trypsin. This trypsin-activated receptor is distinct from that of protease-activated receptor-2, because the response to trypsin was unaffected by protease-activated receptor-2 overexpression or knockdown.     

Slo1 caveolin-binding motif, a mechanism of caveolin-1-Slo1 interaction regulating Slo1 surface expression

The large conductance, voltage- and Ca2+-activated potassium (MaxiK, BK) channel and caveolin-1 play important roles in regulating vascular contractility. Here, we hypothesized that the MaxiK alpha-subunit (Slo1) and caveolin-1 may interact with each other. Slo1 and caveolin-1 physiological association in native vascular tissue is strongly supported by (i) detergent-free purification of caveolin-1-rich domains demonstrating a pool of aortic Slo1 co-migrating with caveolin-1 to light density sucrose fractions, (ii) reverse co-immunoprecipitation, and (iii) double immunolabeling of freshly isolated myocytes revealing caveolin-1 and Slo1 proximity at the plasmalemma. In HEK293T cells, Slo1-caveolin-1 association was unaffected by the smooth muscle MaxiK beta1-subunit. Sequence analysis revealed two potential caveolin-binding motifs along the Slo1 C terminus, one equivalent, 1007YNMLCFGIY1015, and another mirror image, 537YTEYLSSAF545, to the consensus sequence, varphiXXXXvarphiXXvarphi. Deletion of 1007YNMLCFGIY1015 caused approximately 80% loss of Slo1-caveolin-1 association while preserving channel normal folding and overall Slo1 and caveolin-1 intracellular distribution patterns. 537YTEYLSSAF545 deletion had an insignificant dissociative effect. Interestingly, caveolin-1 coexpression reduced Slo1 surface and functional expression near 70% without affecting channel voltage sensitivity, and deletion of 1007YNMLCFGIY1015 motif obliterated channel surface expression. The results suggest 1007YNMLCFGIY1015 possible participation in Slo1 plasmalemmal targeting and demonstrate its role as a main mechanism for caveolin-1 association with Slo1 potentially serving a dual role: (i) maintaining channels in intracellular compartments downsizing their surface expression and/or (ii) serving as anchor of plasma membrane resident channels to caveolin-1-rich membranes. Because the caveolin-1 scaffolding domain is juxtamembrane, it is tempting to suggest that Slo1-caveolin-1 interaction facilitates the tethering of the Slo1 C-terminal end to the membrane.     

Chemical–Genetic Profiling of Imidazo[1,2-a]pyridines and -Pyrimidines Reveals Target Pathways Conserved between Yeast and Human Cells

Small molecules have been shown to be potent and selective probes to understand cell physiology. Here, we show that imidazo[1,2-a]pyridines and imidazo[1,2-a]pyrimidines compose a class of compounds that target essential, conserved cellular processes. Using validated chemogenomic assays in Saccharomyces cerevisiae, we discovered that two closely related compounds, an imidazo[1,2-a]pyridine and -pyrimidine that differ by a single atom, have distinctly different mechanisms of action in vivo. 2-phenyl-3-nitroso-imidazo[1,2-a]pyridine was toxic to yeast strains with defects in electron transport and mitochondrial functions and caused mitochondrial fragmentation, suggesting that compound 13 acts by disrupting mitochondria. By contrast, 2-phenyl-3-nitroso-imidazo[1,2-a]pyrimidine acted as a DNA poison, causing damage to the nuclear DNA and inducing mutagenesis. We compared compound 15 to known chemotherapeutics and found resistance required intact DNA repair pathways. Thus, subtle changes in the structure of imidazo-pyridines and -pyrimidines dramatically alter both the intracellular targeting of these compounds and their effects in vivo. Of particular interest, these different modes of action were evident in experiments on human cells, suggesting that chemical–genetic profiles obtained in yeast are recapitulated in cultured cells, indicating that our observations in yeast can: (1) be leveraged to determine mechanism of action in mammalian cells and (2) suggest novel structure–activity relationships.