Myostatin is a key mediator between energy metabolism and endurance capacity of skeletal muscle

Myostatin (Mstn) participates in the regulation of skeletal muscle size and has emerged as a regulator of muscle metabolism. Here, we hypothesized that lack of myostatin profoundly depresses oxidative phosphorylation-dependent muscle function. Toward this end, we explored Mstn/ mice as a model for the constitutive absence of myostatin and AAV-mediated overexpression of myostatin propeptide as a model of myostatin blockade in adult wild-type mice. We show that muscles from Mstn/ mice, although larger and stronger, fatigue extremely rapidly. Myostatin deficiency shifts muscle from aerobic toward anaerobic energy metabolism, as evidenced by decreased mitochondrial respiration, reduced expression of PPAR transcriptional regulators, increased enolase activity, and exercise-induced lactic acidosis. As a consequence, constitutively reduced myostatin signaling diminishes exercise capacity, while the hypermuscular state of Mstn/ mice increases oxygen consumption and the energy cost of running. We wondered whether these results are the mere consequence of the congenital fiber-type switch toward a glycolytic phenotype of constitutive Mstn/ mice. Hence, we overexpressed myostatin propeptide in adult mice, which did not affect fiber-type distribution, while nonetheless causing increased muscle fatigability, diminished exercise capacity, and decreased Pparb/d and Pgc1a expression. In conclusion, our results suggest that myostatin endows skeletal muscle with high oxidative capacity and low fatigability, thus regulating the delicate balance between muscle mass, muscle force, energy metabolism, and endurance capacity.

A dynamic mechanistic model of lactic acid metabolism in the rumen

Current feed evaluation systems for ruminants are too imprecise to describe diets in terms of their acidosis risk. The dynamic mechanistic model described herein arises from the integration of a lactic acid (La) metabolism module into an extant model of whole-rumen function. The model was evaluated using published data from cows and sheep fed a range of diets or infused with various doses of La. The model performed well in simulating peak rumen La concentrations (coefficient of determination = 0.96; root mean square prediction error = 16.96% of observed mean), although frequency of sampling for the published data prevented a comprehensive comparison of prediction of time to peak La accumulation. The model showed a tendency for increased La accumulation following feeding of diets rich in nonstructural carbohydrates, although less-soluble starch sources such as corn tended to limit rumen La concentration. Simulated La absorption from the rumen remained low throughout the feeding cycle. The competition between bacteria and protozoa for rumen La suggests a variable contribution of protozoa to total La utilization. However, the model was unable to simulate the effects of defaunation on rumen La metabolism, indicating a need for a more detailed description of protozoal metabolism. The model could form the basis of a feed evaluation system with regard to rumen La metabolism.

Modelling acidosis and the cell cycle in multicellular tumour spheroids

A partial differential equation model is developed to understand the effect that nutrient and acidosis have on the distribution of proliferating and quiescent cells and dead cell material (necrotic and apopotic) within a multicellular tumour spheroid. The rates of cell quiescence and necrosis depend upon the local nutrient and acid concentrations and quiescent cells are assumed to consume less nutrient and produce less acid than proliferating cells. Analysis of the differences in nutrient consumption and acid production by quiescent and proliferating cells shows low nutrient levels do not necessarily lead to increased acid concentration via anaerobic metabolism. Rather, it is the balance between proliferating and quiescent cells within the tumour which is important; decreased nutrient levels lead to more quiescent cells, which produce less acid than proliferating cells. We examine this effect via a sensitivity analysis which also includes a quantification of the effect that nutrient and acid concentrations have on the rates of cell quiescence and necrosis.

Selection of potential probiotic lactic acid bacteria from fermented olives by in vitro tests

The present study aims to evaluate the probiotic potential of lactic acid bacteria (LAB) isolated from naturally fermented olives and select candidates to be used as probiotic starters for the improvement of the traditional fermentation process and the production of newly added value functional foods. Seventy one (71) lactic acid bacterial strains (17 Leuconostoc mesenteroides, 1 Ln. pseudomesenteroides, 13 Lactobacillus plantarum, 37 Lb. pentosus, 1 Lb. paraplantarum, and 2 Lb. paracasei subsp. paracasei) isolated from table olives were screened for their probiotic potential. Lb. rhamnosus GG and Lb. casei Shirota were used as reference strains. The in vitro tests included survival in simulated gastrointestinal tract conditions, antimicrobial activity (against Listeria monocytogenes, Salmonella Enteritidis, Escherichia coli O157:H7), Caco-2 surface adhesion, resistance to 9 antibiotics and haemolytic activity. Three (3) Lb. pentosus, 4 Lb. plantarum and 2 Lb. paracasei subsp. paracasei strains demonstrated the highest final population (>8 log cfu/ml) after 3 h of exposure at low pH. The majority of the tested strains were resistant to bile salts even after 4 h of exposure, while 5 Lb. plantarum and 7 Lb. pentosus strains exhibited partial bile salt hydrolase activity. None of the strains inhibited the growth of the pathogens tested. Variable efficiency to adhere to Caco-2 cells was observed. This was the same regarding strains' susceptibility towards different antibiotics. None of the strains exhibited β-haemolytic activity. As a whole, 4 strains of Lb. pentosus, 3 strains of Lb. plantarum and 2 strains of Lb. paracasei subsp. paracasei were found to possess desirable in vitro probiotic properties similar to or even better than the reference probiotic strains Lb. casei Shirota and Lb. rhamnosus GG. These strains are good candidates for further investigation both with in vivo studies to elucidate their potential health benefits and in olive fermentation processes to assess their technological performance as novel probiotic starters.

Enhancing the crystallization and orientation of electrospinning poly (lactic acid) (PLLA) by combining with additives

PLLA is a thermoplastic biopolymer and can be used in industrial applications for medical and filtration applications. The brittleness of PLLA is attributed to slow crystallization rates and its glass transition temperature (Tg) is high (60 °C); for this reason, its applications are limited. The orientation, morphology, and crystal structure of the electrospun fibers was investigated by SEM, POM, DSC, FTIR, XRD, and SAXS. Combining with additives leads to a large decrease of fiber diameter, viscosity, and changes of fiber morphology and crystal structure compared to pure PLLA. DSC showed that the Tg of PLLA decreased about 15 °C and there was no change in relaxation enthalpy by the addition of plasticizer. FT-IR indicate a strong interaction between PLLA and additives; a new band appears in the PLLA blend at 1,756 cm−1 at room temperature as a crystalline band without any annealing. In addition, WAXD indicated that the intensities of the two peaks at (200/110) and (203) increased for the blend at room temperature without any annealing in comparison with PLLA; this means that PHB crystallizes in the amorphous region of PLLA. The POM experiments agree with the results from DSC, FTIR, and WAXS measurements, confirming that adding PHB results in an increase in the number of nuclei with much smaller spherulites and enhances the crystallization behavior of this material, thereby improving its potential for applications.

Zea mays annexins modulate cytosolic free Ca2+ and generate a Ca2+-permeable conductance

Regulation of reactive oxygen species and cytosolic free calcium ([Ca2+](cyt)) is central to plant function. Annexins are small proteins capable of Ca2+-dependent membrane binding or membrane insertion. They possess structural motifs that could support both peroxidase activity and calcium transport. Here, a Zea mays annexin preparation caused increases in [Ca2+] cyt when added to protoplasts of Arabidopsis thaliana roots expressing aequorin. The pharmacological profile was consistent with annexin activation (at the extracellular plasma membrane face) of Arabidopsis Ca2+-permeable nonselective cation channels. Secreted annexins could therefore modulate Ca2+ influx. As maize annexins occur in the cytosol and plasma membrane, they were incorporated at the intracellular face of lipid bilayers designed to mimic the plasma membrane. Here, they generated an instantaneously activating Ca2+-permeable conductance at mildly acidic pH that was sensitive to verapamil and Gd3+ and had a Ca2+-to-K+ permeability ratio of 0.36. These results suggest that cytosolic annexins create a Ca2+ influx pathway directly, particularly during stress responses involving acidosis. A maize annexin preparation also demonstrated in vitro peroxidase activity that appeared independent of heme association. In conclusion, this study has demonstrated that plant annexins create Ca2+-permeable transport pathways, regulate [Ca2+] cyt, and may function as peroxidases in vitro.

Developing a quantitative approach for determining the in vitro prebiotic potential of dietary oligosaccharides

Prebiotics are nondigestible carbohydrates that beneficially affect the host by selectively stimulating the growth and/or activity of one, or a limited number of, bacteria present in the colon. The selected genera should have the capacity to improve host health (e.g. Bifidobacterium, Lactobacillus). To help identify preferred types, for inclusion into the diet, a quantitative equation [measure of the prebiotic effect (MPE)] is suggested. This will help evaluate, in vitro, the fermentation of dietary carbohydrates and compare their prebiotic effect. Although the approach is not meant to define health values, it is formulated to better inform the choice of prebiotic. It therefore, compares measurements of bacterial changes through the determination of maximum growth rates of predominant groups present in faeces, rate of substrate assimilation and the production of lactic, acetic, propionic and butyric acids. The equation will allow further in vitro comparisons of MPE, leading towards further studies (e.g. in humans) to determine the success of dietary intervention. (C) 2004 Federation of European Microbiological Societies. Published by Elsevier B.V. All rights reserved.

Clostridium bolteae sp. nov., isolated from human sources

Seven obligately anaerobic, gram-positive, rod-shaped, spore-forming organisms isolated from human sources were characterized using phenotypic and molecular taxonomic methods. Comparative 16S rRNA gene sequencing showed that the strains were genetically highly related to each other (displaying >99% sequence similarity) and represent a previously unknown sub-line within the Clostridium coccoides rRNA group of organisms. Strains of the unidentified bacterium used carbohydrate as fermentable substrates, producing acetic acid and lactic acid as the major products of glucose metabolism. The closest described species to the novel bacterium corresponded to Clostridium clostridioforme, although a 16S rRNA sequence divergence of 3% demonstrated they represent different species. Genomic DNA-DNA pairing studies confirmed the separateness of the unknown species and Clostridium clostridioforme. Based on phenotypic and phylogenetic evidence, it is therefore proposed that the unknown bacterium, be classified as Clostridium bolteae sp. nov. The type strain of Clostridium bolteae is WAL 16351(T) (= ATCC(T) = BAA-613(T), CCUG(T) = 46953(T)).

Selective fermentation of gentiobiose-derived oligosaccharides by human gut bacteria and influence of molecular weight

Gentiooligosaccharides and alternansucrase gentiobiose acceptor products were fractionated by their degree of polymerization (DP) on a Bio-Gel P2 column. Fractions were characterized by matrix-assisted laser desorption ionization time-of-flight mass spectroscopy, and incubated with human faecal bacteria under anaerobic conditions at 37 degrees C. The growth of predominant gut bacteria on the oligosaccharides was evaluated by fluorescence in situ hybridization and a prebiotic index (PI) was calculated. Lower DP gentiooligosaccharides (DP2-3) showed the highest selectivity (PI of 4.89 and 3.40, respectively), whereas DP4-5 alternansucrase gentiobiose acceptor products generated the greatest values (PI of 5.87). The production of short-chain fatty acids was also determined during the time course of the reactions. The mixture of DP6-10 alternansucrase gentiobiose acceptor products generated the highest levels of butyric acid but the lowest levels of lactic acid. Generally, for similar molecular weights, alternansucrase gentiobiose acceptor products gave higher PI values than gentiooligosaccharides.