Maximal lengthening contractions increase p70 S6 kinase phosphorylation in human skeletal muscle in the absence of nutritional supply

The aim of this study was to compare the training stimuli of eccentric (lengthening) and concentric (shortening) contractions regarding the effect on signaling enzymes involved in protein synthesis. Ten male subjects performed 4 x 6 maximal eccentric contractions on one leg followed by 4 x 6 maximal concentric contractions on the other. Six additional subjects performed the same protocol, but with maximal concentric and submaximal eccentric exercise of equal force to that of the maximal concentric contractions. Muscle biopsy samples were taken from the vastus lateralis before, immediately after, and 1 and 2 h after exercise in both legs. The average peak force produced during the maximal eccentric exercise was 31% higher than during the maximal concentric exercise, 2,490 (+/-100) vs. 1,894 (+/-108) N (P < 0.05). The maximal eccentric contractions led to two- to eightfold increases in the phosphorylation of p70 S6 kinase (p70(S6k)) and the ribosomal protein S6 that persisted for 2 h into recovery but no significant changes in phosphorylation of Akt or mammalian target of rapamycin (mTOR). Maximal concentric and submaximal eccentric contractions did not induce any significant changes in Akt, mTOR, p70(S6k), or S6 phosphorylation up to 2 h after the exercise. The results indicate that one session of maximal eccentric contractions activates p70(S6k) in human muscle via an Akt-independent pathway and suggest that maximal eccentric contractions are more effective than maximal concentric contractions in stimulating protein synthesis in the absence of a nutritional intake, an effect that may be mediated through a combination of greater tension and stretching of the muscle.     

Coaggregation between freshwater bacteria within biofilm and planktonic communities

The coaggregation ability of bacteria isolated from a freshwater biofilm was compared to those derived from the coexisting planktonic population. Twenty-nine morphologically distinct bacterial strains were isolated from a 6-month-old biofilm, established in a glass tank under high-shear conditions, and 15 distinct strains were isolated from the associated re-circulating water. All 44 strains were identified to genus or species level by 16S rDNA sequencing. The 29 biofilm strains belonged to 14 genera and 23.4% of all the possible pair-wise combinations coaggregated. The 15 planktonic strains belonged to seven genera and only 5.8% of all the possible pair-wise combinations coaggregated. Therefore, compared to the planktonic population, a greater proportion of the biofilm strains coaggregated. It is proposed that coaggregation influences biofilm formation and species diversity in freshwater under high shear.     

Biofilm formation on the surface of monazite and xenotime during bioleaching

Microbial attachment and biofilm formation is a ubiquitous behaviour of microorganisms and is the most crucial prerequisite of contact bioleaching. Monazite and xenotime are two commercially exploitable minerals containing rare earth elements (REEs). Bioleaching using phosphate solubilizing microorganisms is a green biotechnological approach for the extraction of REEs. In this study, microbial attachment and biofilm formation of Klebsiella aerogenes ATCC 13048 on the surface of these minerals were investigated using confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). In a batch culture system, K. aerogenes was able to attach and form biofilms on the surface of three phosphate minerals. The microscopy records showed three distinctive stages of biofilm development for K. aerogenes commencing with initial attachment to the surface occurring in the first minutes of microbial inoculation. This was followed by colonization of the surface and formation of a mature biofilm as the second distinguishable stage, with progression to dispersion as the final stage. The biofilm had a thin-layer structure. The colonization and biofilm formation were localized toward physical surface imperfections such as cracks, pits, grooves and dents. In comparison to monazite and xenotime crystals, a higher proportion of the surface of the high-grade monazite ore was covered by biofilm which could be due to its higher surface roughness. No selective attachment or colonization toward specific mineralogy or chemical composition of the minerals was detected. Finally, in contrast to abiotic leaching of control samples, microbial activity resulted in extensive microbial erosion on the high-grade monazite ore.     

Effect of T- and B-lymphocyte mitogens on interactions between lymphocytes and macrophages.

The mitogenic response of murine T cells ² to Con A, S-Con A and PHA was found to be macrophage-dependent. Optimal mitogenic responses were obtained when macrophage-depleted T-cell populations were reconstituted with 5% normal peritoneal macro-phages. Studies were carried out to investigate the effect of T- and B-cell mitogens on in vitro physical interactions between murine lymphocytes and macrophages. This was done by determining the number of T- or B cells binding to macrophages in the absence and in the presence of T- and B cell mitogens, and comparing the results of these experiments with the induction of lymphocyte proliferation. Con A increased the binding of T cells to macrophages when used in mitogenic doses (1–5 μg/ml). Dose response experiments showed that the same dose of Con A which produced maximal mitogenic stimulation also induced the greatest number of T cells to bind to macrophages. Nonmitogenic doses of Con A (20–50 μg/ml) did not enhance the binding of T cells, while identical doses of S-Con A both induced T cell mitogenesis and increased the number of T cells bound to macrophages. Similar results were obtained with PHA. None of the B-cell mitogens tested (LPS, EPO 127 and LAgl) increased the binding of either T or B cells to macrophages. PWM, which is mitogenic for both T and B cells, increased the binding of T cells to macrophages, but not that of B cells. In brief, the four T-cell mitogens tested (Con A, S-Con A, PHA, and PWM) induced specific physical interactions between T cells and macrophages, while none of the B-cell mitogens had any effect on the physical interactions between either B or T cells and macrophages when used in mitogenic doses.     

Pre-PCR processing

Polymerase chain reaction (PCR) is recognized as a rapid, sensitive, and specific molecular diagnostic tool for the analysis of nucleic acids. However, the sensitivity and kinetics of diagnostic PCR may be dramatically reduced when applied directly to biological samples, such as blood and feces, owing to PCR-inhibitory components. As a result, pre-PCR processing procedures have been developed to remove or reduce the effects of PCR inhibitors. Pre-PCR processing comprises all steps prior to the detection of PCR products, that is, sampling, sample preparation, and deoxyribonucleic acid (DNA) amplification. The aim of pre-PCR processing is to convert a complex biological sample with its target nucleic acids/cells into PCR-amplifiable samples by combining sample preparation and amplification conditions. Several different pre-PCR processing strategies are used: (1) optimization of the DNA amplification conditions by the use of alternative DNA polymerases and/or amplification facilitators, (2) optimization of the sample preparation method, (3) optimization of the sampling method, and (4) combinations of the different strategies. This review describes different pre-PCR processing strategies to circumvent PCR inhibition to allow accurate and precise DNA amplification.     

Divergent phenotypic patterns and commitment to apoptosis of Caco-2 cells during spontaneous and butyrate-induced differentiation

Caco-2 cells differentiate spontaneously when cultured in confluence and on exposure to the physiologically relevant short-chain fatty acid, butyrate. This study aimed to compare the phenotype induced by these pathways and their relations to cell turnover. Caco-2 cells were treated with butyrate at a nontoxic concentration of 2 mM for 3 days, or allowed to spontaneously differentiate for 0-21 days. Brush border hydrolase activities and carcinoembryonic antigen (CEA) expression, transepithelial resistance and dome formation, expression of components of the urokinase system, and cell turnover by flow cytometry, and the degree of DNA fragmentation were quantified. Butyrate induced increases in alkaline phosphatase activity and CEA expression but not the activities of other hydrolases, while culture alone induced progressive increases in the activities/expression of all markers. Butyrate induced a significantly greater increase in transepithelial resistance (TER) than occurred during culture alone but the densities of domes were similar. Butyrate induced a ninefold increase in urokinase receptor expression and twofold increase in urokinase activity, while culture alone induced a significantly smaller increase in receptor expression, an increase in plasminogen activator inhibitor-1 but no change in activity. While both stimuli induced cell cycle arrest, only butyrate increased the proportion of cells undergoing apoptosis. In conclusion, differentiation of Caco-2 cells can proceed along multiple pathways but does not necessarily lead to apoptosis. The phenotypic changes during spontaneous differentiation mimic those that occur in normal colonic epithelial cells in vivo during their migration from the crypt base to neck, while butyrate-induced effects more closely follow those occurring when normal colonic epithelial cells migrate from crypt neck to the surface compartment.