Increased rate of force development and neural drive of human skeletal muscle following resistance training.

The maximal rate of rise in muscle force [rate of force development (RFD)] has important functional consequences as it determines the force that can be generated in the early phase of muscle contraction (0-200 ms). The present study examined the effect of resistance training on contractile RFD and efferent motor outflow ("neural drive") during maximal muscle contraction. Contractile RFD (slope of force-time curve), impulse (time-integrated force), electromyography (EMG) signal amplitude (mean average voltage), and rate of EMG rise (slope of EMG-time curve) were determined (1-kHz sampling rate) during maximal isometric muscle contraction (quadriceps femoris) in 15 male subjects before and after 14 wk of heavy-resistance strength training (38 sessions). Maximal isometric muscle strength [maximal voluntary contraction (MVC)] increased from 291.1 +/- 9.8 to 339.0 +/- 10.2 N. m after training. Contractile RFD determined within time intervals of 30, 50, 100, and 200 ms relative to onset of contraction increased from 1,601 +/- 117 to 2,020 +/- 119 (P < 0.05), 1,802 +/- 121 to 2,201 +/- 106 (P < 0.01), 1,543 +/- 83 to 1,806 +/- 69 (P < 0.01), and 1,141 +/- 45 to 1,363 +/- 44 N. m. s(-1) (P < 0.01), respectively. Corresponding increases were observed in contractile impulse (P < 0.01-0.05). When normalized relative to MVC, contractile RFD increased 15% after training (at zero to one-sixth MVC; P < 0.05). Furthermore, muscle EMG increased (P < 0.01-0.05) 22-143% (mean average voltage) and 41-106% (rate of EMG rise) in the early contraction phase (0-200 ms). In conclusion, increases in explosive muscle strength (contractile RFD and impulse) were observed after heavy-resistance strength training. These findings could be explained by an enhanced neural drive, as evidenced by marked increases in EMG signal amplitude and rate of EMG rise in the early phase of muscle contraction.     

Purification of antibodies against N-homocysteinylated proteins by affinity chromatography on Nomega-homocysteinyl-aminohexyl-Agarose

Modification with homocysteine (Hcy)-thiolactone leads to the formation of N-Hcy-Lys-protein. Although N-Hcy-Lys-proteins are immunogenic, pure antibodies have not yet been obtained. Here we describe synthesis and application of Nomega-homocysteinyl-aminohexyl-Agarose for affinity purification of anti-N-Hcy-Lys-protein antibodies. Nomega-homocysteinyl-aminohexyl-Agarose was prepared by N-homocysteinylation of omega-aminohexyl-Agarose with Hcy-thiolactone. Immune serum was obtained from rabbits inoculated with N-Hcy-Lys-keyhole limpet hemocyanine and IgG fraction prepared by chromatography on protein A-Agarose. Anti-N-Hcy-Lys-protein IgG was adsorbed on Nomega-homocysteinyl-aminohexyl-Agarose column at pH 8.6 and eluted with a pH 2.3 buffer. Enzyme-linked immunosorbent assays demonstrate that the antibody recognizes specifically N-homocysteinylated variants of hemoglobin, albumin, transferrin, and antitrypsin.     

Phylogeny of Passerida (Aves: Passeriformes) based on nuclear and mitochondrial sequence data

Passerida is a monophyletic group of oscine passerines that includes almost 3500 species (about 36%) of all bird species in the world. The current understanding of higher-level relationships within Passerida is based on DNA-DNA hybridizations [C.G. Sibley, J.E. Ahlquist, Phylogeny and Classification of Birds, 1990, Yale University Press, New Haven, CT]. Our results are based on analyses of 3130 aligned nucleotide sequence data obtained from 48 ingroup and 13 outgroup genera. Three nuclear genes were sequenced: c-myc (498-510 bp), RAG-1 (930 bp), and myoglobin (693-722 bp), as well one mitochondrial gene; cytochrome b (879 bp). The data were analysed by parsimony, maximum-likelihood, and Bayesian inference. The African rockfowl and rockjumper are found to constitute the deepest branch within Passerida, but relationships among the other taxa are poorly resolved--only four major clades receive statistical support. One clade corresponds to Passeroidea of [C.G. Sibley, B.L. Monroe, Distribution and Taxonomy of Birds of the World, 1990, Yale University Press, New Haven, CT] and includes, e.g., flowerpeckers, sunbirds, accentors, weavers, estrilds, wagtails, finches, and sparrows. Starlings, mockingbirds, thrushes, Old World flycatchers, and dippers also group together in a clade corresponding to Muscicapoidea of Sibley and Monroe [op. cit.]. Monophyly of their Sylvioidea could not be corroborated--these taxa falls either into a clade with wrens, gnatcatchers, and nuthatches, or one with, e.g., warblers, bulbuls, babblers, and white-eyes. The tits, penduline tits, and waxwings belong to Passerida but have no close relatives among the taxa studied herein.     

Impact of emotion on consciousness: positive stimuli enhance conscious reportability

Emotion and reward have been proposed to be closely linked to conscious experience, but empirical data are lacking. The anterior cingulate cortex (ACC) plays a central role in the hedonic dimension of conscious experience; thus potentially a key region in interactions between emotion and consciousness. Here we tested the impact of emotion on conscious experience, and directly investigated the role of the ACC. We used a masked paradigm that measures conscious reportability in terms of subjective confidence and objective accuracy in identifying the briefly presented stimulus in a forced-choice test. By manipulating the emotional valence (positive, neutral, negative) and the presentation time (16 ms, 32 ms, 80 ms) we measured the impact of these variables on conscious and subliminal (i.e. below threshold) processing. First, we tested normal participants using face and word stimuli. Results showed that participants were more confident and accurate when consciously seeing happy versus sad/neutral faces and words. When stimuli were presented subliminally, we found no effect of emotion. To investigate the neural basis of this impact of emotion, we recorded local field potentials (LFPs) directly in the ACC in a chronic pain patient. Behavioural findings were replicated: the patient was more confident and accurate when (consciously) seeing happy versus sad faces, while no effect was seen in subliminal trials. Mirroring behavioural findings, we found significant differences in the LFPs after around 500 ms (lasting 30 ms) in conscious trials between happy and sad faces, while no effect was found in subliminal trials. We thus demonstrate a striking impact of emotion on conscious experience, with positive emotional stimuli enhancing conscious reportability. In line with previous studies, the data indicate a key role of the ACC, but goes beyond earlier work by providing the first direct evidence of interaction between emotion and conscious experience in the human ACC.     

Characterization of thin gelatin hydrogel membranes with balloon properties for dynamic tissue engineering

Cell or tissue stretching and strain are present in any in vivo environment, but is difficult to reproduce in vitro. Here, we describe a simple method for casting a thin (about 500 μm) and soft (about 0.3 kPa) hydrogel of gelatin and a method for characterizing the mechanical properties of the hydrogel simply by changing pressure with a water column. The gelatin is crosslinked with mTransglutaminase and the area of the resulting hydrogel can be increased up 13-fold by increasing the radial water pressure. This is far beyond physiological stretches observed in vivo. Actuating the hydrogel with a radial force achieves both information about stiffness, stretchability, and contractability, which are relevant properties for tissue engineering purposes. Cells could be stretched and contracted using the gelatin membrane. Gelatin is a commonly used polymer for hydrogels in tissue engineering, and the discovered reversible stretching is particularly interesting for organ modeling applications.     

Protein Paucimannosylation Is an Enriched N‐Glycosylation Signature of Human Cancers

While aberrant protein glycosylation is a recognized characteristic of human cancers, advances in glycoanalytics continue to discover new associations between glycoproteins and tumorigenesis. This glycomics‐centric study investigates a possible link between protein paucimannosylation, an under‐studied class of human N‐glycosylation [Man_1‐3GlcNAc₂Fuc_0‐1], and cancer. The paucimannosidic glycans (PMGs) of 34 cancer cell lines and 133 tissue samples spanning 11 cancer types and matching non‐cancerous specimens are profiled from 467 published and unpublished PGC‐LC‐MS/MS N‐glycome datasets collected over a decade. PMGs, particularly Man_2‐3GlcNAc₂Fuc₁, are prominent features of 29 cancer cell lines, but the PMG level varies dramatically across and within the cancer types (1.0–50.2%). Analyses of paired (tumor/non‐tumor) and stage‐stratified tissues demonstrate that PMGs are significantly enriched in tumor tissues from several cancer types including liver cancer (p = 0.0033) and colorectal cancer (p = 0.0017) and is elevated as a result of prostate cancer and chronic lymphocytic leukaemia progression (p < 0.05). Surface expression of paucimannosidic epitopes is demonstrated on human glioblastoma cells using immunofluorescence while biosynthetic involvement of N‐acetyl‐β‐hexosaminidase is indicated by quantitative proteomics. This intriguing association between protein paucimannosylation and human cancers warrants further exploration to detail the biosynthesis, cellular location(s), protein carriers, and functions of paucimannosylation in tumorigenesis and metastasis.     

Mechanical Signaling on the Single Protein Level Studied Using Steered Molecular Dynamics

Efficient communication between the cell and its external environment is of the utmost importance to the function of multicellular organisms. While signaling events can be generally characterized as information exchange by means of controlled energy conversion, research efforts have hitherto mainly been concerned with mechanisms involving chemical and electrical energy transfer. Here, we review recent computational efforts addressing the function of mechanical force in signal transduction. Specifically, we focus on the role of steered molecular dynamics (SMD) simulations in providing details at the atomic level on a group of protein domains, which play a fundamental role in signal exchange by responding properly to mechanical strain. We start by giving a brief introduction to the SMD technique and general properties of mechanically stable protein folds, followed by specific examples illustrating three general regimes of signal transfer utilizing mechanical energy: purely mechanical, mechanical to chemical, and chemical to mechanical. Whenever possible the physiological importance of the example at hand is stressed to highlight the diversity of the processes in which mechanical signaling plays a key role. We also provide an overview of future challenges and perspectives for this rapidly developing field.     

The vertical distribution of N and K uptake in relation to root distribution and root uptake capacity in mature Quercus robur, Fagus sylvatica and Picea abies stands

We have measured the uptake capacity of nitrogen (N) and potassium (K) from different soil depths by injecting ¹⁵N and caesium (Cs; as an analogue to K) at 5 and 50 cm soil depth and analysing the recovery of these markers in foliage and buds. The study was performed in monocultures of 40-year-old pedunculate oak (Quercus robur), European beech (Fagus sylvatica) and Norway spruce (Picea abies (L.) Karst.) located at an experimental site in Palsgård, Denmark. The markers were injected as a solution through plastic tubes around 20 trees of each species at either 5 or 50 cm soil depth in June 2003. After 65 days foliage and buds were harvested and the concentrations of ¹⁵N and Cs analysed. The recovery of ¹⁵N in the foliage and buds tended to be higher from 5 than 50 cm soil depth in oak whereas they where similar in spruce and beech after compensation for differences in immobilization of ¹⁵N in the soil. In oak more Cs was recovered from 5 than from 50 cm soil depth whereas in beech and spruce no difference could be detected. Out of the three investigated tree species, oak was found to have the lowest capacity to take up Cs at 50 cm soil depth compared to 5 cm soil depth also after compensating for differences in discrimination against Cs by the roots. The uptake capacity from 50 cm soil depth compared with 5 cm was higher than expected from the root distribution except for K in oak, which can probably be explained by a considerable overlap of the uptake zones around the roots and mycorrhizal hyphae in the topsoil. The study also shows that fine roots at different soil depths with different physiological properties can influence the nutrient uptake of trees. Estimates of fine root distribution alone may thus not reflect the nutrient uptake capacity of trees with sufficient accuracy. Our study shows that deep-rooted trees such as oak may have lower nutrient uptake capacity at deeper soil layers than more shallow-rooted trees such as spruce, as we found no evidence that deep-rooted trees obtained proportionally more nutrients from deeper soil layers. This has implications for models of nutrient cycling in forest ecosystems that use the distribution of roots as the sole criterion for predicting uptake of nutrients from different soil depths.