Usnic acid,as a biotic factor,changes the ploidy level in mosses

Lichens and mosses often share the same environmental conditions where they compete for substrate and other essential factors. Lichens use secondary metabolites as allelochemicals to repel surrounding plants and potential rivals. In mosses, endoreduplication leads to the occurrence of various ploidy levels in the same individual and has been suggested as an adaptation to abiotic stresses. Here, we show that also biotic factors such as usnic acid, an allelochemical produced by lichens, directly influenced the level of ploidy in mosses. Application of usnic acid changed the nuclei proportion and significantly enhanced the endoreduplication index in two moss species, Physcomitrella patens and Pohlia drummondii. These investigations add a new aspect on secondary metabolites of lichens which count as biotic factors and affect ploidy levels in mosses.     

Context-dependent memory: colour versus odour

An olfactory stimulus and a visual stimulus were employed in a context- dependent memory study using a prose passage as the to-be-remembered item. Ninety-five university students (aged 17-35 years) learned the passage of prose in the presence of one of the stimuli and were then asked to recall the passage with the original context either reinstated or not reinstated. The results revealed a significant context-dependent memory effect for the olfactory cue but not for the visual cue. They demonstrate support for the effectiveness of odours as context cues and it is suggested that context-dependent memory processes may underlie the formation and retrieval of odour-evoked autobiographical memories.      

The effect of N-nitroso carcinogens and triazenes on protein synthesis in cell-free systems

The effect of a series of carcinogenic nitrosamines, alkylnitrosoureas and alkaryltriazenes on enzymatic reactions involved in protein synthesis was studied in cell-free systems from rat liver. The addition of most compounds stimulated the formation of aminoacyl-tRNA complex in test systems from rat liver whereas analogous preparations from Escherichia coli did not show this effect. The polymerization of phenylalanine and the binding of aminoacyl-tRNA to ribosome were only slightly and apparently non-specifically inhibited in the presence of the test compounds. On the other hand, the binding of nRNA to ribosome was markedly stimulated after the addition of most carcinogens tested. It appears that the carcinogens intervene specifically with one of the early steps in peptide initiation. Since the binding of mRNA to ribosome is known to be an important rate-limiting step in protein synthesis, the N-nitroso carcinogens and triazenes may thus control the expression of genetic message at the translation level.     

Expression and localization of caveolins during postnatal development in rat heart: implication of thyroid hormone.

Caveolins modulate signaling pathways involved in cardiac development. Caveolin-1 exists in two isoforms: the beta-isoform derivates from an alternative translational start site that creates a protein truncated by 31 amino acids, mainly expressed in endothelial cells, whereas caveolin-3 is present in muscle cells. Our aim was to define caveolin distribution and expression during cardiac postnatal development using immunofluorescence and Western blotting. Caveolin-3 sarcolemmal labeling appeared as dotted lines from days 1 to 5 and as continuous lines after 14 days of age. Caveolin-3 expression, low at birth, increased (4-fold) to reach a maximum (P < 0.05) by day 5 and then decreased to stabilize in adults. Total caveolin-1 and its alpha-isoform were codistributed at birth in endothelial and smooth muscle cells; afterward, only the caveolin-1alpha labeling became limited to endothelium. Quantitative analysis indicated a similar temporal pattern of both total caveolin-1 and caveolin-1alpha expression, suggesting that caveolin-1alpha and -1beta are coregulated; the caveolin-1alpha levels increased fourfold by day 5 to reach a maximum by day 14 (P < 0.05). Tyrosine-14-caveolin-1 phosphorylation, low at birth, increased suddenly around day 14 (8-fold vs. day 1) and returning afterward to basal level. Because the T3/T4 level is maximal by day 14, caveolin-1 expression/phosphorylation profiles were analyzed in hypothyroid heart. The levels of caveolin-1alpha and consequently tyrosine-14-caveolin-1 phosphorylation, but not that of caveolin-3, decreased (50%) in hypothyroid 14-day-old rats. Our data demonstrate that, during postnatal cardiac growth, 1) caveolins are distinctly regulated, and 2) thyroid hormones are involved in caveolin-1alpha expression.     

Blood plasma model predictions for the proposed bone-seeking radiopharmaceutical [Sn]Sn(IV)-N,N′,N′-trimethylenephosphonate-poly(ethyleneimine)

In an attempt to elucidate the in vivo stability of the prospective radiopharmaceutical [^117mSn]Sn(IV)-PEI-MP, where PEI-MP stands for N,N′,N′-trimethylenephosphonate-polyethyleneimine, glass electrode potentiometry was used to determine the stability constants of the Sn⁴⁺ ion as complexed with a variety of physiological amino acids. In addition, linear free energy relationship (LFER) correlation plots were used to extrapolate the constants of the major blood plasma ligands, based on data from Cu²⁺, Pb²⁺, and Zn²⁺. In so doing, a thermodynamic model of blood plasma was established for Sn⁴⁺ from which the complexation tendencies of Sn⁴⁺ were predicted in the event of the intravenous administration of such a drug. It was found that the Sn(IV)-PEI-MP could succumb to competition by the glutamine amino acid, which forms more stable complex(es), whilst the PEI-MP gets taken up largely by Ca²⁺. Also, this study shows the value of the in vitro experiments and modeling performed for radiopharmaceutical research and for attempts to reduce the number of animal experiments.     

Complete genome sequence of the haloaromatic acid-degrading bacterium Achromobacter xylosoxidans A8

Achromobacter xylosoxidans strain A8 was isolated from soil contaminated with polychlorinated biphenyls. It can use 2-chlorobenzoate and 2,5-dichlorobenzoate as sole sources of carbon and energy. This property makes it a good starting microorganism for further development toward a bioremediation tool. The genome of A. xylosoxidans consists of a 7-Mb chromosome and two large plasmids (98 kb and 248 kb). Besides genes for the utilization of xenobiotic organic substrates, it contains genes associated with pathogenesis, toxin production, and resistance. Here, we report the complete genome sequence.     

The role of MHC class I allele Mamu-A*07 during SIVmac239 infection

Virus-specific CD8(+) T cells play an important role in controlling HIV/SIV replication. These T cells recognize intracellular pathogen-derived peptides displayed on the cell surface by individual MHC class I molecules. In the SIV-infected rhesus macaque model, five Mamu class I alleles have been thoroughly characterized with regard to peptide binding, and a sixth was shown to be uninvolved. In this study, we describe the peptide binding of Mamu-A1*007:01 (formerly Mamu-A*07), an allele present in roughly 5.08% of Indian-origin rhesus macaques (n?=?63 of 1,240). We determined a preliminary binding motif by eluting and sequencing endogenously bound ligands. Subsequently, we used a positional scanning combinatorial library and panels of single amino acid substitution analogs to further characterize peptide binding of this allele and derive a quantitative motif. Using this motif, we selected and tested 200 peptides derived from SIV(mac)239 for their capacity to bind Mamu-A1*007:01; 33 were found to bind with an affinity of 500?nM or better. We then used PBMC from SIV-infected or vaccinated but uninfected, A1*007:01-positive rhesus macaques in IFN-γ Elispot assays to screen the peptides for T-cell reactivity. In all, 11 of the peptides elicited IFN-γ(+) T-cell responses. Six represent novel A1*007:01-restricted epitopes. Furthermore, both Sanger and ultradeep pyrosequencing demonstrated the accumulation of amino acid substitutions within four of these six regions, suggestive of selective pressure on the virus by antigen-specific CD8(+) T cells. Thus, it appears that Mamu-A1*007:01 presents SIV-derived peptides to antigen-specific CD8(+) T cells and is part of the immune response to SIV(mac)239.     

Evolutionary significance of hybridization in Onosma (Boraginaceae): analyses of stabilized hemisexual odd polyploids and recent sterile hybrids

Interspecific hybridization is an important evolutionary force promoting plant speciation. In the genus Onosma, one of three main evolutionary lineages presumably evolved by hybrid speciation. The assumed hybrid lineage (Heterotricha) consists of two species complexes with bimodal karyotypes containing different numbers of large (L) and small (S) chromosomes, the tetraploid Onosma pseudoarenaria (2n = 12 L + 14S) and the triploid Onosma arenaria (2n = 12 L + 8S). The latter represents a rare case of hemisexual, asymmetrically compensating allopolyploids. Representatives of the other two lineages of the genus, Haplotricha (2n = 12 L) and Asterotricha (2n = 14S), have been considered to be the ancestral taxa of O. pseudoarenaria and O. arenaria, although this has yet to be investigated critically. In the present study, we examined genetic [amplified fragment length polymorphism (AFLP), internal transcribed spacer (ITS) , and chloroplast (cp)DNA)], reproductive (pollen viability and seed production) and cytogenetic (chromosome counts, genome size assessment) patterns to resolve the hypothesized allopolyploid formations in the Heterotricha group, single or polytopic allopolyploid origins, as well as ongoing interspecific gene flow as one piece of evidence for understanding past hybrid speciation events in the genus. Discordant patterns in maternally inherited cpDNA (Heterotricha accessions bearing the haplotypes related to asterotrichous species) and the nuclear ITS and AFLP markers (Heterotricha clustering with haplotrichous Onosma fastigiata), as well as karyological features, support the hybrid origin of the stabilized Heterotricha lineage. Genetic variation that is both large and geographically correlated indicates multiple origins of Heterotricha allopolyploids or, less likely, a single origin with recurring introgression from the progenitor species. The nuclear markers and cytogenetic features also provide evidence for the ongoing hybridization between O. arenaria and Onosma echioides (2n = 14S), which gives rise to sterile triploids of 2n = 6 L + 15S. We contrast the two cases of triploids with LLS (hemisexual O. arenaria from the stabilized Heterotricha lineage) and LSS (recent sterile hybrids) karyotypes, which could help to understand the mechanisms ensuring the establishment and reproductive fitness of the odd allopolyploids in Onosma. © 2014 The Linnean Society of London, Biological Journal of the Linnean Society, 2014, 112 , 89–107.     

Magnesium Transport Across the Basolateral Plasma Membrane of the Fish Enterocyte

In tilapia (Oreochromis mossambicus) intestine, Mg²⁺ transport across the epithelium involves a transcellular, Na⁺- and Na⁺/K⁺-ATPase dependent pathway. In our search for the Mg²⁺ extrusion mechanism of the basolateral compartment of the enterocyte, we could exclude Na⁺/Mg²⁺ antiport or ATP-driven transport. Evidence is provided, however, that Mg²⁺ movement across the membrane is coupled to anion transport. In basolateral plasma membrane vesicles, an inwardly directed Cl⁻ gradient stimulated Mg²⁺ uptake (as followed with the radionuclide ²⁷Mg) twofold. As Cl⁻-stimulated uptake was inhibited by the detergent saponin and by the ionophore A23187, Mg²⁺ may be accumulated intravesicularly above chemical equilibrium. Valinomycin did not affect uptake, suggesting that electroneutral symport activity occurred. The involvement of anion coupled transport was further indicated by the inhibition of Mg²⁺ uptake by the stilbene derivative, 4,4′-diisothiocyanato-stilbene-2,2′-disulfonic acid. Kinetic analyses of the Cl⁻-stimulated Mg²⁺ uptake yielded a K _m (Mg²⁺) of 6.08 ± 1.29 mmol · l⁻¹ and a K _m (Cl⁻) of 26.5 ± 6.5 mmol · l⁻¹, compatible with transport activity at intracellular Mg²⁺- and Cl⁻-levels. We propose that Mg²⁺ absorption in the tilapia intestine involves an electrically neutral anion symport mechanism. Received: 19 January 1996/Revised: 1 August 1996