Yarın diye bir şey...

Taha Toros Arşivi, Dosya No: 262-Tarık Buğr

Structure of bryozoan communities in an Antarctic glacial fjord (Admiralty Bay, South Shetlands)

Bryozoans are among the most important groups of the Southern Ocean benthic macrofauna, both in terms of species richness and abundance. However, there is a considerable lack of ecological research focused on their distribution patterns and species richness on smaller scale, especially in the soft bottom habitats of Antarctic glacial fjords. The aim of this study was to describe those patterns in the Admiralty Bay. Forty-nine Van Veen grab samples were collected at the depth range from 15 to 265 m, in the summer season of 1979/1980, at three sites distributed along the main axis of the fjord. Among 53 identified species of bryozoans, 32 were recorded in the Admiralty Bay for the first time. The most common and abundant species were Himantozoum antarcticum, Inversiula nutrix and Nematoflustra flagellata. Genera such as Arachnopusia, Cellarinella and Osthimosia were the most speciose taxa. It was demonstrated that depth was important for the distribution of the bryozoans. More than half of the recorded species were found only below 70 m. An influence of glacial disturbance was reflected in the dominance structure of colony growth-forms. The inner region of the fjord was dominated almost entirely by encrusting species, while the diversity of bryozoan growth-forms in less disturbed areas was much higher. In those sites the highest percentage of branched, tuft like species represented by buguliform and flustriform zoaria was observed.The study was supported by a grant of Polish Ministry of Science and Higher Education No. 51/N-IPY/2007/0 as well as Census of Antarctic Marine Life Project. Krzysztof Pabis was also partially supported by University of Lodz internal funds. This research was also supported by the Polish Geological Institute-National Research Institute during the realization of the project numbered 40.2900.0903.18.0 titled “Bryozoan assemblage of Admiralty Bay—richness, diversity and abundance.” Urszula Hara is deeply grateful to Leszek Giro (Micro-area Analyses Laboratory at the Polish Geological Institute-National Research Institute, Warsaw), for providing SEM assistance during the project. We also want to thank two anonymous reviewers for their suggestions that helped us improve this article. Thanks are also due to Magdalena Błażewicz-Paszkowycz for language correction and polishing the final version of the manuscript

Calpain-mediated proteolysis as driver and modulator of polyglutamine toxicity

Among posttranslational modifications, directed proteolytic processes have the strongest impact on protein integrity. They are executed by a variety of cellular machineries and lead to a wide range of molecular consequences. Compared to other forms of proteolytic enzymes, the class of calcium-activated calpains is considered as modulator proteases due to their limited proteolytic activity, which changes the structure and function of their target substrates. In the context of neurodegeneration and - in particular - polyglutamine disorders, proteolytic events have been linked to modulatory effects on the molecular pathogenesis by generating harmful breakdown products of disease proteins. These findings led to the formulation of the $\textit {toxic fragment hypothesis}$, and calpains appeared to be one of the key players and auspicious therapeutic targets in Huntington disease and Machado Joseph disease. This review provides a current survey of the role of calpains in proteolytic processes found in polyglutamine disorders. Together with insights into general concepts behind $\textit {toxic fragments}$ and findings in polyglutamine disorders, this work aims to inspire researchers to broaden and deepen the knowledge in this field, which will help to evaluate calpain-mediated proteolysis as a unifying and therapeutically targetable posttranslational mechanism in neurodegeneration

Investigating the Effectiveness of Phosphonate Additives in Hindering the Calcium Sulfate Dihydrate Scale Formation

The effects of 20 ppm 1-hydroxy ethylidene-1,1-diphosphonic acid (HEDP), amino trimethylene phosphonic acid (ATMP), polyamino poly(ether methylene phosphonic acid) (PAPEMP), diethylene triamine penta (methylene phosphonic acid) (DTPMPA), and bis(hexamethylene triamine penta (methylene phosphonic acid)) (BHMTPMPA) on the room-temperature crystallization of calcium sulfate dihydrate (gypsum) were investigated by in situ UV–vis, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma optical emission spectrometry (ICP-OES), and scanning electron microscopy (SEM) techniques. A comparison between additive-containing and additive-free experiments showed that BHMTPMPA was the most efficient antiscalant by completely inhibiting crystallization. Due to the chain length of the BHMTPMPA molecule, the crystallization kinetics decreased to a larger extent than DTPMPA. The increase in pH of the solution from ∼4 to ∼7 positively enhanced the efficiency of the phosphonates in inhibiting crystallization. Our results revealed that partially deprotonated phosphonate additives were strongly associated with gypsum crystals and/or potentially taken up into the crystal matrix, resulting in a sudden and sharp increase in turbidity plots. Furthermore, phosphonate additives altered the thin, twinned gypsum crystals into thick needles