Beneficial effect of fluorocarbon emulsion media on the function of neuromuscular preparations in vitro

The effects of liquid fluorocarbons as bathing media were determined by use of in vitro neuromuscular preparations. Rat hemidiaphragms were bathed in either oxygenated fluorocarbon (FC) emulsion or standard oxygenated Krebs solution. Contractile force in response to simple supramaximal nerve stimuli as well as to high frequency stimulation was greater, while twitch:tetanus ratio was smaller in FC emulsion. With such medium, post-tetanic potentiation of contraction was also more consistently observed. Indirectly stimulated diaphragms survived longer in FC emulsion. After cessation of oxygenation, oxygen tension (ρO(2)) of the medium declined more rapidly with Krebs than with FC emulsion; ρO(2) directly correlated with force of contraction. Similarly, in the chick biventer cervicis preparation, FC emulsion enhanced nerve-stimulated force of contraction; returning the preparation to standard Krebs solution reversed this phenomenon. Dose-resonse curves of muscle contraction in response to acetycholine and KCl administration were shifted upward during FC emulsion superfusion. Frequency of miniature endplate potentials was lower in FC emulsion than that observed in Krebs solution, measured from the same cell of the rat diaphragm. Resting membrane potentials were also greater in muscle cells sampled from FC emulsion-bathed preparations. These data suggest that FC emulsion is superior to standard Krebs solution as a bathing medium for in vitro neuromuscular preparations by virtue of the high solubility of oxygen in it.     

Universal foliage-stem scaling across environments and species in dicot trees: plasticity, biomechanics and Corner's Rules

Trees range from small-leaved, intricately branched species with slender stems to large-leaved, coarsely branched ones with thick stems. We suggest a mechanism for this pattern, known as Corner's Rules, based on universal scaling. We show similar crown area–stem diameter scaling between trunks and branches, environments, and species spanning a wide range of leaf size and stem biomechanics. If crown and stem maintain metabolically driven proportionality, but similar amounts of photosynthates are produced per unit crown area, then the greater leaf spacing in large-leaved species requires lower density stem tissue and, meeting mechanical needs, thicker stems. Congruent with this scenario, we show a negative relationship between leaf size and stem Young's modulus. Corner's Rules emerge from these mutual adjustments, which suggest that adaptive studies cannot consider any of these features independently. The constancy of scaling despite environmental challenges identifies this trait constellation as a crucial axis of plant diversification.     

A role for human Sp alpha as a pattern recognition receptor

Human Sp alpha is a soluble protein belonging to group B of the scavenger receptor cysteine-rich (SRCR) superfamily for which little functional information is available. It is expressed by macrophages present in lymphoid tissues (spleen, lymph node, thymus, and bone marrow), and it binds to myelomonocytic and lymphoid cells, which suggests that it may play an important role in the regulation of the innate and adaptive immune systems. In the present study we show that recombinant human Sp alpha (rSp alpha) binds to the surface of several gram-positive and gram-negative bacterial strains. Competition studies indicated that such binding is mediated by the recognition of lipoteichoic acid (LTA) and lipopolysaccharide (LPS), respectively, through nonoverlapping sites on the Sp alpha molecule. The most conserved part of LPS (2-keto-3-deoxyoctulosonic acid and lipid A) was shown to be involved in the recognition by Sp alpha. Bacterial binding studies using the SRCR domain 1 of Sp alpha showed that this domain retains both the LPS and LTA binding activities, indicating that both bacterial interacting sites are retained in a single SRCR domain. Furthermore, rSp alpha induced aggregation of gram-positive and gram-negative bacteria strains. On the other hand, rSp alpha inhibited tumor necrosis factor-alpha secretion by human monocytes stimulated with LPS or LTA. Binding of Sp alpha to conserved components of bacterial surfaces and modulation of the monocyte response indicate that this molecule is an active constituent of the innate immune response of the host.     

Effect of ozone treatment on reactive oxygen species and adenosine production during hepatic ischemia-reperfusion

This study investigates whether ozone could confer protection from hepatic ischemia reperfusion by modifying the accumulation of adenosine and xanthine during ischemia. A significant increase in both adenosine and xanthine accumulation was observed as a consequence of ATP degradation during hepatic ischemia. Adenosine exerts a protective effect on hepatic ischemia reperfusion injury since the elimination of endogenous adenosine accumulation with adenosine deaminase increased the hepatic injury associated with this process. On the other hand, the high xanthine levels observed after ischemia could exert deleterious effects during reperfusion due to reactive oxygen species generation from xanthine oxidase. The administration of allopurinol, an inhibitor of xanthine oxidase, attenuated the increase in reactive oxygen species and transaminase levels observed after hepatic reperfusion. Ozone treatment in liver maintained adenosine levels similar to those found after ischemia but led to a marked reduction in xanthine accumulation. In order to evaluate the role of both adenosine and xanthine, we tried to modify the protection confered by ozone, by modifying the concentrations of adenosine and xanthine. The metabolization of endogenous adenosine after ischemia abolished the protective effect conferred by ozone. When xanthine was administered previous to ozone treatment, the protection conferred by adenosine disappeared, showing both postischemic reactive oxygen species and transaminase levels similar to those found after hepatic ischemia reperfusion. Ozone would confer protection against the hepatic ischemia reperfusion injury by the accumulation of adenosine that in turns benefits the liver and by blocking the xanthine/xanthine oxidase pathway for reactive oxygen species generation.     

On-line monitoring of yeast cell growth by impedance spectroscopy

The application of impedance spectroscopy to estimate on-line cell concentration was studied. The estimation was based on the relative variation between electrical impedance measured at low (10 kHz) and high frequencies (10 MHz). Studies were carried out to characterise the influence of changes in physical and chemical parameters on the impedance measurement. Two different possibilities to perform on-line measurements were tested: a simple set-up, based on an in situ probe, gave good results but was not suitable for high agitation and aeration rates. An ex situ flow-through on-line measuring cell was used to overcome these problems, showing a better performance. The use of this set-up for the growth monitorisation of a Saccharomyces cerevisiae culture showed an efficient performance, having the correlation between estimated and measured S. cerevisiae a Pearson coefficient of 0.999.     

Short human occupations in the Middle Palaeolithic level I of the Abric Romani rock-shelter (Capellades, Barcelona, Spain)

This paper presents a multidisciplinary study on the size of the occupied surfaces, provisioning strategies and behaviour planning at the Romani rock-shelter, using the Middle Palaeolithic record of the level i. This level is dated around 46.000 BP through U/Th ages. A behavioural interpretation is proposed, which emphasises the activities and the systemic value of the archaeological artefacts and structures. Occupation patterns are identified on the basis of the accumulations formed by human activities. These archaeological accumulations, consisting of artefacts and hearths, are easily defined visually as spatial units. The relationships between these accumulations, established by means of refitted remains, indicate that differences can be established between: 1) small and medium-sized occupation surfaces; 2) restricted and diversified provisioning strategies. This variability suggests that different modes of occupation are represented in the same archaeological level. The human activities reveal the generalization of fire technology. In almost all sizes of the occupation surfaces, the exploitation of vegetal resources near the Abric Romani marks the threshold of the restricted provisioning strategy. Limited use and fragmented knapping activities are recorded in the lithic assemblage. Faunal remains show differential transport. The exploitation of lithic, faunal and vegetal resources characterizes the diversified provisioning strategy. The small occupation surfaces and restricted provisioning strategies suggest short settlements in the Abric Romani. This shorter occupation model complements the longer diversified provisioning strategy recorded in both small and medium-sized occupied surfaces. The selection of precise elements for transport and the possible deferred consumption in the diversified provision strategy suggest an individual supply. In this respect, Neanderthal occupations in the Romani rock-shelter show a direct relation to: 1) hunting strategic resources; 2) high, linear mobility.     

Thesaurus-based disambiguation of gene symbols

Background  

Massive text mining of the biological literature holds great promise of relating disparate information and discovering new knowledge. However, disambiguation of gene symbols is a major bottleneck.     

Functional studies of signaling pathways in peri-implantation development of the mouse embryo by RNAi

Background

Studies of gene function in the mouse have relied mainly on gene targeting via homologous recombination. However, this approach is difficult to apply in specific windows of time, and to simultaneously knock-down multiple genes. Here we report an efficient method for dsRNA-mediated gene silencing in late cleavage-stage mouse embryos that permits examination of phenotypes at post-implantation stages.

Results

We show that introduction of Bmp4 dsRNA into intact blastocysts by electroporation recapitulates the genetic Bmp4 null phenotype at gastrulation. It also reveals a novel role for Bmp4 in the regulation the anterior visceral endoderm specific gene expression and its positioning. We also show that RNAi can be used to simultaneously target several genes. When applied to the three murine isoforms of Dishevelled, it leads to earlier defects than previously observed in double knock-outs. These include severe delays in post-implantation development and defects in the anterior midline and neural folds at headfold stages.

Conclusion

Our results indicate that the BMP4 signalling pathway contributes to the development of the anterior visceral endoderm, and reveal an early functional redundancy between the products of the murine Dishevelled genes. The proposed approach constitutes a powerful tool to screen the functions of genes that govern the development of the mouse embryo.     

Experimental inoculation of conventional pigs with porcine reproductive and respiratory syndrome virus and porcine circovirus 2

Postweaning multisystemic wasting syndrome (PMWS) is a disease of nursery and fattening pigs characterized by growth retardation, paleness of the skin, dyspnea, and increased mortality rates. Porcine circovirus 2 (PCV2) has been demonstrated to be the cause of PMWS. However, other factors are needed for full development of the syndrome, and porcine reproductive and respiratory syndrome virus (PRRSV) infection has been suggested to be one of them. Twenty-four conventional 5-week-old pigs were distributed in four groups: control (n = 5), PRRSV inoculated (n = 5), PCV2 inoculated (n = 7), and PRRSV and PCV2 inoculated (n = 7). The two groups inoculated with PRRSV showed growth retardation. Pigs inoculated with both PRRSV and PCV2 had increased rectal temperature. One of these pigs developed wasting, had severe respiratory distress, and died. The most important microscopic lesion in pigs inoculated with PCV2 was lymphocyte depletion with histiocytic infiltration of the lymphoid organs, more severe and in a wider range of tissues in doubly inoculated pigs. Interstitial pneumonia was observed in the three inoculated groups. PCV2 nucleic acid was found by in situ hybridization in larger amounts and in a wider range of lymphoid tissues in PRRSV- and PCV2-inoculated than in PCV2-inoculated pigs. TaqMan PCR was performed to quantify the PCV2 loads in serum during the experiment. PCV2 loads were higher in doubly inoculated pigs than in pigs inoculated with PCV2 alone. These findings indicate that severe disease can be reproduced in conventional 5-week-old pigs by inoculation of PRRSV and PCV2. Moreover, these results support the hypothesis that PRRSV infection enhances PCV2 replication.