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Search Results: 1 - 10 of 4388 matches for " Boris Martinac "
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"Smart fats", healthy brain and function of lipid-sensing NMDA receptors  [PDF]
Anna Kloda, Boris Martinac
Advances in Biological Chemistry (ABC) , 2012, DOI: 10.4236/abc.2012.22013
Abstract: NMDA receptor channels play a significant role in learning and memory and their dysfunction can cause neuronal cell death leading to dementia. Research had shown that lipids change the risk for dementia, especially some omega-3 lipids appear to lower Alz-heimer’s risk, yet only limited research exists on the modulation of NMDA receptor channels by lipids. Here we review recent literature concerning molecular determinants that influence the NMDA receptor channel gating via membrane lipids and fatty acids with profound significance for understanding how altered NMDA signalling leads to neuronal cell death linked to age-related dementia’s. Future discovery of lipid-like modulators of NMDA receptor function offer the potential for the development of new bioceu-ticals and affordable nutritional supplements to combat neuronal degeneration as well as to promote well being and healthy aging.
Common evolutionary origins of mechanosensitive ion channels in Archaea, Bacteria and cell-walled Eukarya
Anna Kloda,Boris Martinac
Archaea , 2002, DOI: 10.1155/2002/419261
Abstract: The ubiquity of mechanosensitive (MS) channels triggered a search for their functional homologs in Archaea. Archaeal MS channels were found to share a common ancestral origin with bacterial MS channels of large and small conductance, and sequence homology with several proteins that most likely function as MS ion channels in prokaryotic and eukaryotic cell-walled organisms. Although bacterial and archaeal MS channels differ in conductive and mechanosensitive properties, they share similar gating mechanisms triggered by mechanical force transmitted via the lipid bilayer. In this review, we suggest that MS channels of Archaea can bridge the evolutionary gap between bacterial and eukaryotic MS channels, and that MS channels of Bacteria, Archaea and cell-walled Eukarya may serve similar physiological functions and may have evolved to protect the fragile cellular membranes in these organisms from excessive dilation and rupture upon osmotic challenge.
Povezanost rizi nih i za titnih faktora s prilagodbom roditelja djece koja boluju od cerebralne paralize
Tamara Martinac Dor?i?
Psychological Topics , 2012,
Abstract: Cilj je ovog istra ivanja ispitati prediktore prilagodbe roditelja na kroni nu bolest djeteta uklju uju i relevantne varijable unutar modela rizi nih i za titnih faktora (Wallander i Varni, 1998) i to na uzorku i majki i o eva djece s cerebralnom paralizom. U ispitivanje su bili uklju eni roditelji 77 djece s cerebralnom paralizom koja poha aju redovne vrti e ili kole, a u manjoj mjeri posebne ustanove u osam hrvatskih gradova. Ukupno je sudjelovalo 59 bra nih parova – roditelja djece s cerebralnom paralizom te 18 roditelja bez bra nog partnera (ukupno 75 majki i 61 otac). Rezultati ovog istra ivanja pokazuju da pojedini rizi ni i za titni faktori imaju zna ajne izravne efekte na izra enost psihi kih simptoma kod majki i o eva djece s cerebralnom paralizom. Kao zna ajni pojedina ni prediktori su se, ovisno o spolu roditelja, izdvojili problemi u pona anju djeteta, roditeljski stres i neuroticizam. Ve a percepcija problema u pona anju djeteta, intenzivniji roditeljski stres i izra eniji neuroticizam povezani su s lo ijom prilagodbom roditelja. Utvr en je i zna ajni moderatorski efekt pesimizma i obiteljskog funkcioniranja na odnos izme u intenziteta roditeljskog stresa i izra enosti psihi kih simptoma kod majki i/ili o eva djece s cerebralnom paralizom: nizak pesimizam i visoka obiteljska kohezivnost i prilagodljivost imaju za titnu ulogu u situacijama intenzivnoga roditeljskog stresa. Utvr ena je medijacijska uloga roditeljskog stresa u odnosu izme u problema u pona anju kod djeteta i izra enosti psihi kih simptoma kod majki.
Inhibitory Control Over Ca2+ Sparks via Mechanosensitive Channels Is Disrupted in Dystrophin Deficient Muscle but Restored by Mini-Dystrophin Expression
Martin D. H. Teichmann, Frederic v. Wegner, Rainer H. A. Fink, Jeffrey S. Chamberlain, Bradley S. Launikonis, Boris Martinac, Oliver Friedrich
PLOS ONE , 2008, DOI: 10.1371/journal.pone.0003644
Abstract: Background In dystrophic skeletal muscle, osmotic stimuli somehow relieve inhibitory control of dihydropyridine receptors (DHPR) on spontaneous sarcoplasmic reticulum elementary Ca2+ release events (ECRE) in high Ca2+ external environments. Such ‘uncontrolled’ Ca2+ sparks were suggested to act as dystrophic signals. They may be related to mechanosensitive pathways but the mechanisms are elusive. Also, it is not known whether truncated dystrophins can correct the dystrophic disinhibition. Methodology/Principal Findings We recorded ECRE activity in single intact fibers from adult wt, mdx and mini-dystrophin expressing mice (MinD) under resting isotonic conditions and following hyper-/hypo-osmolar external shock using confocal microscopy and imaging techniques. Isotonic ECRE frequencies were small in wt and MinD fibers, but were markedly increased in mdx fibers. Osmotic challenge dramatically increased ECRE activity in mdx fibers. Sustained osmotic challenge induced marked exponential ECRE activity adaptation that was three times faster in mdx compared to wt and MinD fibers. Rising external Ca2+ concentrations amplified osmotic ECRE responses. The eliminated ECRE suppression in intact osmotically stressed mdx fibers was completely and reversibly resuscitated by streptomycine (200 μM), spider peptide GsMTx-4 (5 μM) and Gd3+ (20 μM) that block unspecific, specific cationic and Ca2+ selective mechanosensitive channels (MsC), respectively. ECRE morphology was not substantially altered by membrane stress. During hyperosmotic challenge, membrane potentials were polarised and a putative depolarisation through aberrant MsC negligible excluding direct activation of ECRE through tubular depolarisation. Conclusions/Significance Dystrophin suppresses spontaneous ECRE activity by control of mechanosensitive pathways which are suggested to interact with the inhibitory DHPR loop to the ryanodine receptor. MsC-related disinhibition prevails in dystrophic muscle and can be resuscitated by transgenic mini-dystrophin expression. Our results have important implications for the pathophysiology of DMD where abnormal MsC in dystrophic muscle confer disruption of microdomain Ca2+ homeostasis. MsC blockers should have considerable therapeutic potential if more muscle specific compounds can be found.
Single Molecule FRET Reveals Pore Size and Opening Mechanism of MscL
Yong Wang,Yanxin Liu,Hannah A. DeBerg,Takeshi Nomura,Melinda Tonks Hoffman,Paul R. Rohde,Klaus Schulten,Boris Martinac,Paul R. Selvin
Quantitative Biology , 2014, DOI: 10.7554/elife.01834
Abstract: The mechanosensitive channel of large conductance, which serves as a model system for mechanosensitive channels, has previously been crystallized in the closed form, but not in the open form. Ensemble measurements and electrophysiological sieving experiments show that the open-diameter of the channel pore is >25{\AA}, but the exact size and whether the conformational change follows a helix-tilt or barrel-stave model are unclear. Here we report measurements of the distance changes on liposome-reconstituted MscL transmembrane {\alpha}-helices, using a "virtual sorting" single-molecule fluorescence energy transfer. We observed directly that the channel opens via the helix-tilt model and the open pore reaches 2.8 nm in diameter. In addition, based on the measurements, we developed a molecular dynamics model of the channel structure in the open state which confirms our direct observations.
Effect of TiO2 on the Sintering Process of Magnesium Oxide from Seawater
Martinac, V.,Labor, M.,Jaki?, J.,Petric, N.
Kemija u Industriji , 2010,
Abstract: This study examines the effect of the addition of TiO2 on the properties of magnesium oxide obtained from seawater by substoichiometrical precipitation with 80 % of the stoichiometrically required quantity of dolomite lime as the precipitation agent. Magnesium oxide obtained from seawater by substoichiometrical precipitation contains boron(III) oxide as an impurity. During the precipitation of magnesium hydroxide, the boron present in seawater (in the form of non-dissociated orthoboric acid H3BO3, and partly as borate ion H2BO3 –) adsorbs onto the magnesium hydroxide precipitate, and therefore has to be reduced as much as possible using the appropriate method of rinsing the magnesium hydroxide precipitate. B2O3 is an undesirable admixture in seawater magnesium oxide. Specifically, the properties of special purpose magnesium oxide, i. e. high strength magnesium oxide, are affected significantly by the content of boron in the product. Good quality sintered magnesium oxide contains a very small amount ofB2O3. The impurity should not exceed w(B2O3) = 0.005 % in refractory magnesium oxide.The combined method of rinsing the magnesium hydroxide precipitate (3+2) was used in sample preparation, i. e. rinsing by decanting was done three times with alkalized distilled water of pH = 12.50 and twice with distilled water of pH = 6.74. Multiple rinsing on filter paper (five times) was done using the same rinsing agent (fresh distilled water of pH = 6.74). The MgO (80 % precipitation) samples were then subjected to isothermal and activated sintering without TiO2addition, as well as with the addition of TiO2, w(TiO2) =5 and 8 %, at the temperature of 1700 oC for 1 hour, with the aim of determining the properties of these samples primarily with regard to the B2O3content in the samples after sintering. The results indicate that the addition of TiO2strongly affects the reduction of the B2O3content during activated sintering of seawater magnesium oxide, and that the samples can be characterized as refractory material with very low B2O3 content. The addition of TiO2, w(TiO2)=5 %, is sufficient to bind the present CaO and thereby lead to greater evaporation of B2O3 in the process of activated sintering of seawater magnesium oxide. The samples thickened significantly during sintering, i. e. all the samples examined had a very smallamount of open pores.
The Regulation of Medicines in Croatia - a Contribution to Public Health
Tomi?, S,Filipovi? Su?i?, A,Ili? Martinac, A
Kemija u Industriji , 2010,
Abstract: The regulatory system for medicinal products includes the existence of a legislative framework and a medicines agency as the regulatory body. The legislative framework for medicinal products has been amended several times so as to align it with the EU acquis communautaire, where medicinal products represent one of the best regulated and aligned areas. For the purpose of regulating the Croatian medicines market, the Agency for Medicinal Products and Medical Devices was established in 2003 to implement the procedure of granting marketing authorisation for medicinal products, to supervise the adverse reactions of medicinal products, to conduct laboratory tests of the quality of medicines and vaccines sampled from the market, to issue licences for the manufacture and distribution of medicinal products, to monitor medicine consumption, and to inform about medicines and promote their rational use. Medical devices are regulated under a special act, and the Agency conducts entries into the register in that field and carries out vigilance over medical devices. In this way, products intended for health care on the Croatian market are of the appropriate quality, safety and efficacy, and are under the constant supervision of the competent body that assesses their risk-to-benefit ratio. Upon accession of the Republic of Croatia to full membership in the European Union, the Agency will be included in the European authorisation procedures for medicines, such as the centralised procedure in the European Medicines Agency (EMA), and above all, the mutual recognition procedure and decentralised procedure in which the role of the agencies of EU Member States is greater. This article gives an overview of the most important regulatory activities in the field of medicinal products, and the readiness of the Agency to function in the future integrated European regulatory area.
Relationship between serum lipid concentrations and posttraumatic stress disorder symptoms in soldiers with combat experiences.
Karlovi?? D,Martinac M,Buljan D,Zorici?? Z
Acta Medica Okayama , 2004,
Abstract: The aim of our study was to assess concentrations of serum cholesterol, low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), and triglycerides in soldiers with combat-related posttraumatic stress disorder (PTSD), in comparison with combat-experienced soldiers without PTSD. The second aim of our study was to explore the relationship between PTSD symptoms such as re-experiencing, avoidance, increased arousal, and serum lipid levels. In 53 soldiers with combat-related PTSD and 49 with combat experiences without PTSD, serum cholesterol, LDL-C, HDL-C, and triglycerides were assayed by an enzyme-assay method. Soldiers with combat-related PTSD were found to have significantly higher concentrations of cholesterol (P = 0.001), LDL-C (P = 0.002), and triglycerides (P = 0.001) than soldiers without current PTSD. HDL-C was statistically lower (P < 0.001) in soldiers with combat-related PTSD than in those without PTSD. A positive correlation was found between increased arousal and cholesterol (r = 0.464; P = 0.039), or LDL-C (r = 0.479; P = 0.021) concentrations.
The preparation of dental glass-ceramic composites with controlled fraction of leucite crystals
Martina Mrázová,Alexandra Klou?ková,Martin Pallich,Martinac Kohoutková
Processing and Application of Ceramics , 2008,
Abstract: This work is dealing with synthesis of leucite powder, which can be used for the preparation of dental glassceramic composites by subsequent thermal treatment. Newly developed procedure is based on preparation of dental raw material as a mixture of two separate compounds: the crystalline leucite powder prepared at relatively low temperature and a commercial matrix powder.Hydrothermal synthesis of tetragonal leucite particles (KAlSi2O6) with the average size of about 3 μm was developed in our laboratory. The leucite dental raw material was prepared by mixing of 20 wt.% of synthetic tetragonal leucite with commercial matrix. Dental composites were prepared from the dental raw material by uniaxial pressing and firing up to 960°C. Dilatometric measurements confirmed that the coefficient of thermal expansion increased by 32% when 20 wt.% of the tetragonal leucite was added into the basic matrix. In addition, it was showed that the synthesized leucite powder was suitable for the preparation of leucite composites with controlled coefficient of thermal expansion. High value of the thermal expansion coefficient enables application of prepared composite in metal-ceramics restorations.
Cubic Root Extractors of Gaussian Integers and Their Application in Fast Encryption for Time-Constrained Secure Communication  [PDF]
Boris Verkhovsky
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2011, DOI: 10.4236/ijcns.2011.44024
Abstract: There are settings where encryption must be performed by a sender under a time constraint. This paper de-scribes an encryption/decryption algorithm based on modular arithmetic of complex integers called Gaus-sians. It is shown how cubic extractors operate and how to find all cubic roots of the Gaussian. All validations (proofs) are provided in the Appendix. Detailed numeric illustrations explain how to use the method of digital isotopes to avoid ambiguity in recovery of the original plaintext by the receiver.
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