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Changes in bird communities of Admiralty Bay, King George Island (West Antarctic): insights from monitoring data (1977–1996).
Get PDFAbstract: The paper summarizes results of twenty years of seabird observations carried out between 1977 and 1996 on the western shore of Admiralty Bay (King George Island, South Shetlands, Antarctic). Changes in population size, distribution and phenology of the breeding species as well as the appearance of non-breeding species are reported. A total of 34 species of birds were observed, including 13 breeding species. Among the non-breeding species, four were observed to visit the site regularly, six rarely, and the remaining 11 were observed only occasionally. Among breeding populations, three Pygoscelis penguin species, the main krill consumers, were most numerous. The Adélie Penguin (P. adeliae) dominated among the penguins nesting in the investigated areas, reaching 23,661 breeding pairs in 1978. Two other penguin species were less abundant with population sizes of approximately 7,200 breeding pairs for the Chinstrap Penguin (P. antarcticus) and 3,100 breeding pairs for the Gentoo Penguin (P. papua) in the same year. During the following two decades, breeding populations of pygoscelid species experienced a declining trend and their numbers were reduced by 68.0% for Chinstrap, 67.1% for Gentoo, and 33.9% for Adélie Penguins. The data reported here represent a unique reference basis and provide valuable information about indicator species, suitable for comparison with contemporary observations of bird populations in the Antarctic Peninsula region, a place of rapidly occurring climate changes and intensive harvesting of marine living resources
(S)-2-(4-Chlorobenzoyl)-1,2,3,4-tetrahydrobenzo[e]pyrazino[1,2-a][1,4]diazepine-6,12(11H,12aH)-dione—Synthesis and Crystallographic Studies
Get PDF(S)-2-(4-Chlorobenzoyl)-1,2,3,4-tetrahydrobenzo[e]pyrazino[1,2-a][1,4]diazepine-6,12(11H,
12aH)-dione was obtained in a three-step, one-pot synthesis, starting from optically pure
(S)-2-piperazine carboxylic acid dihydrochloride. Selective acylation of the b-nitrogen atom followed
by condensation with isatoic anhydride and cyclization with HATU/DIPEA to a seven-member
benzodiazepine ring, led to the tricyclic benzodiazepine derivative. Crystallographic studies and
initial biological screening were performed for the title compound
Hypoxic 3D in vitro culture models reveal distinct resistance processes to TKIs in renal cancer cells
Get PDFThe aim of this study is to determine the effect of hypoxia on axitinib and sorafenib-treated renal cell carcinoma (RCC) cells. Hypoxia is a crucial factor influencing transcription process via protein modulation, which was shown i.e. in pancreatic cancer. Until now, hypoxia has been defined as associated with poorer outcome and inducing chemotherapy resistance in solid tumors. The unique phenomenon of pseudo-hypoxia connected with vhl mutation was observed in clear-cell, but not in papillary RCC, and the treatment of this subtype of cancer is still challenging. Despite the introduction of new antiangiogenic targeted therapies (inter alia tyrosine kinase inhibitors, TKIs), patients still develop both primary and acquired resistance. Overcoming resistance to TKIs, also in papillary RCC, may be possible by finding significantly modified protein expression. To do this, hypoxic 3D in vitro models must be developed to mimic both molecular pathways typical for low oxygen tension and cell–cell dynamics in tumor-like spatial structures
The N-terminus of hepcidin is a strong and potentially biologically relevant Cu(II) chelator.
Get PDFHepcidin is an iron regulatory hormone, involved also in immune response in vertebrates. It contains the N-terminal Asp-Thr-His site able to bind Cu(II) ions. A significant discrepancy exist in the literature regarding Cu(II) affinity of this site in hepcidin. Our study focused on the model DTHFPI-NH2 hexapeptide reflecting the N-terminal motif of mature hepcidin Using potentiometry, UV-vis and CD spectroscopies we demonstrated that DTHFPI-NH2 is the strongest Cu(II) binding peptide discovered so far. A competition assay with human serum albumin (HSA) confirmed this high affinity and demonstrated that DTHFPI-NH2. withdraws all Cu(II) from HSA under equimolar concentrations. Based on these results we propose that hepcidin could exist as Cu(II) complex in blood, especially under inflammatory conditions, when its serum concentration is elevated
Small and Smaller—sRNAs and MicroRNAs in the Regulation of Toxin Gene Expression in Prokaryotic Cells: A Mini-Review
Get PDFNon-coding small RNAs (sRNAs) have been identified in the wide range of bacteria
(also pathogenic species) and found to play an important role in the regulation of many processes,
including toxin gene expression. The best characterized prokaryotic sRNAs regulate gene expression
by base pairing with mRNA targets and fall into two broad classes: cis-encoded sRNAs (also called
antisense RNA) and trans-acting sRNAs. Molecules from the second class are frequently considered
as the most related to eukaryotic microRNAs. Interestingly, typical microRNA-size RNA molecules
have also been reported in prokaryotic cells, although they have received little attention up to now.
In this work we have collected information about all three types of small prokaryotic RNAs in the
context of the regulation of toxin gene expression
Polyprenols Are Synthesized by a Plastidial cis-Prenyltransferase and Influence Photosynthetic Performance
Get PDFPlants accumulate a family of hydrophobic polymers known as polyprenols, yet how they are synthesized, where they reside
in the cell, and what role they serve is largely unknown. Using Arabidopsis thaliana as a model, we present evidence for the involvement of a plastidial cis-prenyltransferase (AtCPT7) in polyprenol synthesis. Gene inactivation and RNAi-mediated knockdown of AtCPT7 eliminated leaf polyprenols, while its overexpression increased their content. Complementation tests in the polyprenol-deficient yeast Δrer2 mutant and enzyme assays with recombinant AtCPT7 confirmed that the enzyme synthesizes polyprenols of ~55 carbons in length using geranylgeranyl diphosphate (GGPP) and isopentenyl diphosphate as substrates. Immunodetection and in vivo localization of AtCPT7 fluorescent protein fusions showed that AtCPT7 resides in the stroma of mesophyll chloroplasts. The enzymatic products of AtCPT7 accumulate in thylakoid membranes, and in their absence, thylakoids adopt an increasingly “fluid membrane” state. Chlorophyll fluorescence measurements from the leaves
of polyprenol-deficient plants revealed impaired photosystem II operating efficiency, and their thylakoids exhibited
a decreased rate of electron transport. These results establish that (1) plastidial AtCPT7 extends the length of GGPP to;55 carbons, which then accumulate in thylakoid membranes; and (2) these polyprenols influence photosynthetic performance through their modulation of thylakoid membrane dynamics
Bacteriophages as Factories for Eu2O3 Nanoparticle Synthesis
No full textThe use of phage display to identify peptides with an ability to bind and synthesize Eu2O3 nanoparticles is demonstrated in this report. This is the first report of modified phages specifically binding a lanthanide. The peptides exposed on virions revealed very strong binding to Eu2O3 nanoparticles and the ability to catalyze Eu2O3 nanoparticles' formation from Eu(OH)3 and Eu(NO3)3 solutions. The luminescence emission spectrum of Eu3+ ions indicated that these ions existed mostly in sites deviated from the inversion symmetry in crystalline Eu2O3 aggregates and gelatinous Eu(OH)3 precipitate. The ability of phage-displayed peptides to catalyze formation of Eu2O3 nanoparticles provides a useful tool for a low-cost and effective synthesis of lanthanide nanoparticles, which serve as attractive biomedical sensors or fluorescent labels, among their other applications
First step to eradication of Poa annua L. from Point Thomas Oasis (King George Island, South Shetlands, Antarctica)
Get PDFPoa annua, an alien species reported from the
Antarctic continent and many Antarctic and sub-Antarctic
islands, was accidentally introduced in the vicinity of the
Polish Antarctic Station H. Arctowski. Recently the species
has been found entering native plant communities. In
almost 30 years it dispersed over 250 m from the site it
was first observed and can therefore be considered invasive.
We report the first steps to eradicate the species following
the initial research to quantify the biology, ecology
and genetics of the species. After detailed mapping of all
1439 tussocks located in the Arctowski Station area we
removed 314 tussocks closest to a moss carpet formation
(native plant community of high conservation value). All of
the 49 tussocks growing in the Ecology Glacier forefield
were removed. It is the biggest alien plant eradication act
conducted so far in Antarctica. We plan to continue the
eradication process and monitor the eradicated sites. This
will provide valuable information on impacts and issuesrelated to removal of alien species in the maritime Antarctic
and will help in informing future decisions on management
of other plant invasions in the region. Given the increasing
human traffic to the Antarctic and the associated risks of
invasion our results will be important not only for Arctowski
but also for the whole Antarctic region
Novel layers of RNA polymerase III control affecting tRNA gene transcription in eukaryotes
Get PDFRNA polymerase III (Pol III) transcribes a limited set of short genes in eukaryotes producing abundant small RNAs, mostly tRNA. The originally defined yeast Pol III transcriptome appears to be expanding owing to the application of new methods. Also, several factors required for assembly and nuclear import of Pol III complex have been identified recently. Models of Pol III based on cryo-electron microscopy reconstructions of distinct Pol III conformations reveal unique features distinguishing Pol III from other polymerases. Novel concepts concerning Pol III functioning involve recruitment of general Pol III-specific transcription factors and distinctive mechanisms of transcription initiation, elongation and termination. Despite the short length of Pol III transcription units, mapping of transcriptionally active Pol III with nucleotide resolution has revealed strikingly uneven polymerase distribution along all genes. This may be related, at least in part, to the transcription factors bound at the internal promoter regions. Pol III uses also a specific negative regulator, Maf1, which binds to polymerase under stress conditions; however, a subset of Pol III genes is not controlled by Maf1. Among other RNA polymerases, Pol III machinery represents unique features related to a short transcript length and high transcription efficiency
Lactic acid bacteria — promising vaccine vectors: possibilities, limitations, doubts
Get PDFGram-positive and nonpathogenic lactic acid bacteria (LAB) are considered to be promising candidates for the development of new, safe systems of heterologous protein expression. Additionally, many experiments have shown that specific systemic and mucosal immune responses against selected pathogens can be elicited using modified LAB strains. For that reason they could be a good replacement of classical, often pathogenic, attenuated carriers. This solution offers many advantages in comparison to systemic inoculation, as well as, from immunological and practical points of view. The development of efficient mucosal vaccines is nowadays a priority in modern vaccinology, together with improvement of immunization efficiency, monitoring of antigen production in vivo, determination of optimal dose for vaccination, strain selection and characterization