Relationship between cellular electrolytes and the contraction force of isolated guinea-pig atria with special regard to the extracellular space volume

A micromethod is described which allows the quantitative evaluation of the extracellular space volume of isolated guinea-pig atria (> 15 mg tissue wet weight) by means of an enzymatic estimation of inulin. In addition, the acidic tissue extracts are analysed for the potassium, sodium, magnesium, calcium and ⁴⁵calcium content. Taking into account the individual extracellular space volumes, it is possible to calculate the cellular electrolyte content and relative specific ⁴⁵calcium activity of each atrium. Our experiments reveal under steady state conditions a significant correlation between the force of contraction and the cellular electrolyte content. Atria with a higher contraction force were found to contain a significantly elevated cellular potassium content and a lower content of cellular sodium and calcium than atria with a smaller contraction force. The decrease of cellular calcium content is exclusively caused by the lowering of the fraction of unexchanged tissue calcium. The significance of the results is discussed with respect to the events leading to contraction and relaxation of the heart muscle.     

New role for hPar-1 kinases EMK and C-TAK1 in regulating localization and activity of class IIa histone deacetylases

Class IIa histone deacetylases (HDACs) are found both in the cytoplasm and in the nucleus where they repress genes involved in several major developmental programs. In response to specific signals, the repressive activity of class IIa HDACs is neutralized through their phosphorylation on multiple N-terminal serine residues and 14-3-3-mediated nuclear exclusion. Here, we demonstrate that class IIa HDACs are subjected to signal-independent nuclear export that relies on their constitutive phosphorylation. We identify EMK and C-TAK1, two members of the microtubule affinity-regulating kinase (MARK)/Par-1 family, as regulators of this process. We further show that EMK and C-TAK1 phosphorylate class IIa HDACs on one of their multiple 14-3-3 binding sites and alter their subcellular localization and repressive function. Using HDAC7 as a paradigm, we extend these findings by demonstrating that signal-independent phosphorylation of the most N-terminal serine residue by the MARK/Par-1 kinases, i.e., Ser155, is a prerequisite for the phosphorylation of the nearby 14-3-3 site, Ser181. We propose that this multisite hierarchical phosphorylation by a variety of kinases allows for sophisticated regulation of class IIa HDACs function.     

Investigation of close interactions between sympathetic neural fibres and the follicular dendritic cells network in the mouse spleen

In this study, co-localization between sympathetic neural fibres and the follicular dendritic cells (FDCs) network was observed within the mouse spleen by confocal technology. Immunohistochemical techniques were used to reveal the rare interactions between the FDCs network and sympathetic neural fibres. We estimated the frequency of three kinds of close interactions which could be defined as overlaps, contacts or neural fibres closer than 10 microm from a FDCs network. Using these estimates, a comparison was made between five uninfected mouse strains exhibiting the same Prnpa genotype but showing different incubation periods when inoculated with primary bovine spongiform encephalopathy (BSE)-infected brain. In prion disease, infectivity is generally detected in the spleen much earlier than in the brain, especially after peripheral inoculation. The way by which the infectious agent reaches the central nervous system is still unclear. From the five mouse strains, we obtained differences in the proportion of splenic FDCs networks with close interactions. Our work suggests that the percentage of splenic FDCs networks with at least one sympathetic neural fibre in close vicinity may influence the length of incubation period.     

Limited effects of placental and pituitary growth hormone on cytokine expression in vitro

The hypothesis that growth hormone (GH) can affect immune responses in man has been evaluated by monitoring cytokine expression in cultures from peripheral blood mononuclear cells, by enzyme-linked immunosorbent assay (ELISA) and ribonuclease protection assay, and in tonsillar cells by ELISA. In addition to pituitary GH (GH-N), the placental form (GH-V), differing from pituitary GH by 13 amino acids has also been tested. Only few effects reached statistical significance and were in no case greater than 15%. Pituitary GH slightly reduced IL-5 production and stimulated IFN-gamma production. The latter effect was also observed with prolactin and could thus be induced through the prolactin receptor. It is proposed that GH has no strong effects on the parameters investigated, possibly as a result of redundancy in the cytokine network. Alternatively, effects on leukocytes are mediated by other tissues such as the liver or are clear only in response to stronger challenges.     

Dry mass production and water use of non- and drip irrigated <Emphasis Type="Italic">shape Thuja occidentalis</Emphasis> ‘Brabant’: Field experiments and modeling

Generally, irrigation increases dry mass production (DM) on sandy soils of horticultural crops and at the same time increases the risk of percolation losses of water and chemicals to below the root zone. However, the effects of irrigation are highly site-specific and not easily determined, which hampers the development of proper management tools and guidelines. A two-dimensional soil-water balance model combined with a crop growth model was parameterized and validated, and used to investigate DM and water use of Thuja occidentalis Brabant in a field trial under non- and drip irrigated conditions. Measured leaf DM and leaf area index (LAI) were not affected by irrigation but irrigation increased stem DM and the specific leaf area. Simulated DM and LAI were in good agreement with the measurements. Simulated pressure head followed the measured pressure head, although models performance was better under dry than under wet conditions. Simulation experiments indicated that increasing irrigation threshold levels increased DM production and leaching relatively to no irrigation, when the irrigation threshold level was measured at 0.25m depth.     

An RNA folding method capable of identifying pseudoknots and base triples

MOTIVATION: Recently, we described a Maximum Weighted Matching (MWM) method for RNA structure prediction. The MWM method is capable of detecting pseudoknots and other tertiary base-pairing interactions in a computationally efficient manner (Cary and Stormo, Proceedings of the Third International Conference on Intelligent Systems for Molecular Biology, pp. 75-80, 1995). Here we report on the results of our efforts to improve the MWM method's predictive accuracy, and show how the method can be extended to detect base interactions formerly inaccessible to automated RNA modeling techniques. RESULTS: Improved performance in MWM structure prediction was achieved in two ways. First, new ways of calculating base pair likelihoods have been developed. These allow experimental data and combined statistical and thermodynamic information to be used by the program. Second, accuracy was improved by developing techniques for filtering out spurious base pairs predicted by the MWM program. We also demonstrate here a means by which the MWM folding method may be used to detect the presence of base triples in RNAs. AVAILABILITY: http://www.cshl.org/mzhanglab/tabaska/j axpage. html CONTACT: tabaska@cshl.org      

Leaching of silica and uranium and other quantitative aspects of the lithobiontic colonization in a radioactive thermal spring

The formation of microbial mats by thermophilic organisms on submerged rocks in radioactive thermal springs was followed quantitatively in situ as well as under experimental conditions, by determining the change in dry weight and organic matter as a function of time. Furthermore, the decay of the rock occurring in the springs could be shown to be directly related to the microbial colonization. Early in that process the formation of silicious gels, facilitating the settling of the organisms, could be observed. Simultaneously, this was accompanied by the leaching of silica from the underlying rock. This resulted in the destruction of the rock, which had been altered to a fine-grained dust underneath the colonizing mats; the microorganisms were found to move further downward within this layer. From the heavy metals present in the rock—iron (Fe), copper (Cu), manganese (Mn), uranium (U)— the leaching of uranium could be demonstrated, leading to the acquisition of this metal in the microbial mats in concentrations up to 15.34g/mg dry weight. Direct evidence for the leaching of Si (silicon) and U could be obtained by measurement of these elements after their release from ground rock chips in cultures with microorganisms from the hot springs at 50°C. X-ray analysis of the biomats strongly suggested that Cu, Mn, and Fe are also accumulated.     

Cloning and gene map assignment of the Xiphophorus DNA ligase 1 gene

Fishes represent the stem vertebrate condition and have maintained several gene arrangements common to mammalian genomes throughout the 450 Myr of divergence from a common ancestor. One such syntenic arrangement includes the GPI-PEPD enzyme association on Xiphophorus linkage group IV and human chromosome 19. Previously we assigned the Xiphophorus homologue of the human ERCC2 gene to linkage group U5 in tight association with the CKM locus. CKM is also tightly linked to the ERCC2 locus on human chromosome 19, leading to speculation that human chromosome 19 may have arisen by fusion of two ancestral linkage groups which have been maintained in fishes. To investigate this hypothesis further, we isolated and sequenced Xiphophorus fish genomic regions exhibiting considerable sequence similarity to the human DNA ligase 1 amino acid sequence. Comparison of the fish DNA ligase sequence with those of other species suggests several modes of amino acid conservation in this gene. A 2.2-kb restriction fragment containing part of an X. maculatus DNA ligase 1 exon was used in backcross hybrid mapping with 12 enzyme or RFLP loci. Significant linkage was observed between the nucleoside phosphorylase (NP2) and the DNA ligase (LIG1) loci on Xiphophorus linkage group VI. This assignment suggests that the association of four DNA repair-related genes on human chromosome 19 may be the result of chance chromosomal rearrangements.      

Electro-optical behaviour of CuFe2O4@rGO nanocomposite for nonenzymatic detection of uric acid via the electrochemical method

Uric acid (UA) is a blood and urine component obtained as a metabolic by-product of purine nucleotides. Abnormalities in UA metabolism cause crystal deposition as monosodium urate and lead to various diseases such as gout, hyperuricemia, Lesch–Nyhan syndrome, etc. Monitoring these diseases requires a rapid, sensitive, selective, and portable detection approach. Therefore, this study demonstrates the hydrothermal synthesis of CuFe₂O₄/reduced graphene oxide (rGO) nanocomposite for selective detection of UA. After the nanocomposite synthesis, characterization was performed by X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, UV–visible spectrometry, atomic force spectroscopy, scanning electron microscopy, and electrochemical analysis. Furthermore, from the electrochemical analysis using cyclic voltammetry (CV), kinetic studies were carried out by varying the scan rate to obtain the diffusion coefficient, surface concentration, and rate of charge transfer to achieve a calibration curve that indicates the quasi reversible nature of the fabricated electrode with a linear regression coefficient of oxidation (R²: 0.9992) and reduction (R²: 0.9971) peaks. Moreover, the fabricated nonenzymatic amperometric sensor to detect UA with a linearity (R²: 0.9989) of 1–400 μM was highly sensitive (2.75 × 10⁻⁴ mAμM⁻¹ cm⁻²) and had a lower limit of detection (0.01231 μM) at pH 7.5 in phosphate-buffered saline solution. Therefore, the CuFe₂O₄/rGO/ITO-based nonenzymatic sensor could detect interfering agents and spiked real bovine serum samples with higher sensitivity and selectivity for UA detection.