Frequency and release flux of calcium sparks in rat cardiac myocytes: a relation to RYR gating

Cytosolic calcium concentration in resting cardiac myocytes locally fluctuates as a result of spontaneous microscopic Ca2+ releases or abruptly rises as a result of an external trigger. These processes, observed as calcium sparks, are fundamental for proper function of cardiac muscle. In this study, we analyze how the characteristics of spontaneous and triggered calcium sparks are related to cardiac ryanodine receptor (RYR) gating. We show that the frequency of spontaneous sparks and the probability distribution of calcium release flux quanta of triggered sparks correspond quantitatively to predictions of an allosteric homotetrameric model of RYR gating. This model includes competitive binding of Ca2+ and Mg2+ ions to the RYR activation sites and allosteric interaction between divalent ion binding and channel opening. It turns out that at rest, RYRs are almost fully occupied by Mg2+. Therefore, spontaneous sparks are most frequently evoked by random openings of the highly populated but rarely opening Mg4RYR and CaMg3RYR forms, whereas triggered sparks are most frequently evoked by random openings of the less populated but much more readily opening Ca2Mg2RYR and Ca3MgRYR forms. In both the spontaneous and the triggered sparks, only a small fraction of RYRs in the calcium release unit manages to open during the spark because of the limited rate of Mg2+ unbinding. This mechanism clarifies the unexpectedly low calcium release flux during elementary release events and unifies the theory of calcium signaling in resting and contracting cardiac myocytes

Similarities and differences between 7th and 8th- century pottery as shown by archaeological sites in the vicinity of Hlebine

During 2017 and 2018, as a part of the project TransFER - Iron production along the Drava River in the Roman period and the Middle Ages: Creation and transfer of knowledge, technologies and goods (IP-06-2016- 5047), funded by the Croatian Science Foundation, two archaeological sites in the vicinity of the village Hlebine were excavated. The aim of the research was to explore the bog iron ore smelting workshop at the site of Velike Hlebine and to define features and function of presumed furnaces on the position of Dedanovice, whose existence was acknowledged by the conducted geophysical research. During the course of the excavation, both positions (which are about 600 meters apart), besides the remains connected to smelting activities, brought to light the remains of archaeological structures which can be connected with the remains of settlements. Numerous chipped pottery pieces of various characteristic, belonging mainly to kitchen pots, were discovered within the fillings of the excavated archaeological objects. By comparing their shapes, fabrication, facture, colour, decoration, and other details, it is concluded that, even though the mentioned economic activity took place on both positions at the same time, the ceramic material is significantly different, which suggests it was made in different periods. Comparative ceramic material found within the same region points to a fact that one of the settlements (Dedanovice) was occupied during the first half or the middle of the 7th century, while the other one (Velike Hlebine) operated during the (middle of) 8th century, which was also confirmed by radiocarbon dating

Arheološki nadzor nad radovima rekonstrukcije i izrade pruge kroz Podravinu

U razdoblju između travnja 2021. godine i lipnja 2023. godine Muzej grada Koprivnice provodio je arheološki nadzor nad radovima rekonstrukcije postojećeg i dogradnje drugog kolosijeka dionice pruge Križevci – Koprivnica – državna granica na području Gradova Križevaca i Koprivnice te Općina Sokolovac, Peteranec i Drnje u Koprivničko-križevačkoj županiji. Tijekom provedbe nadzora, uz liniju trase radova, ali i na samoj trasi, zabilježeni su položaji dosad nepoznatih arheoloških lokaliteta iz pretpovijesti, antike i srednjega vijeka. U radu se predstavljaju zabilježeni položaji te preliminarna obrada prikupljenih pokretnih nalaza

Umjetnički izričaj lončara u Podravini tijekom ranog srednjeg vijeka

Kada se govori o ukrašavanju posuda i interpretaciji ukrasa postavlja se pitanje gdje je lončar vidio određeni način ukrašavanja ili je odabrani ukras bio njegov samostalni odabir. Poznato je kako unutar svakog razdoblja postoje karakteristični tipovi i vrste ukrasa koji su zastupljeni, a onda i za određenu kulturu ili zajednicu unutar njega. Također, zajednice se sele i dolaskom na novi prostor ili neposredno iz nekog drugog prostora (trgovinom kao najvjerojatnijim kontaktom) donose svoje tipove ukrasa te/ili preuzimaju tipove ukrasa od drugih zajednica. U arheološkoj se interpretaciji tijekom prapovijesnog razdoblja takve pojave najčešće definiraju kao nove kulture ili njihove druge faze. U razdoblju prapovijesti i antike ukrašavanje je, ali i izrada i namjena pojedinih posuda, imala dublje značenje. Lončari su posude ukrašavali motivima koje su vidjeli oko sebe, u vlastitoj interpretaciji, te na taj način direktno ili simbolički projicirali svoju okolinu. No, što je i bitnije, prikazivali su svoja vjerovanja na medij koji je bio dostupan širokom krugu zajednice. Što se tiče razdoblja srednjega vijeka, vjerujem kako je ukrašavanje posuda manje usmjereno na duhovni, a više na sam umjetnički aspekt te ću se unutar članka orijentirati upravo na njega. Primarno ću se usredotočiti na razdoblje ranoga srednjega vijeka na prostoru Podravine, poglavito na lokalitetima u okolici Torčeca, gdje sam na pojedinim primjerima u izvedbi i odabiru motiva uočio umjetnički izričaj lončara

Terenski pregled trase otpremnog plinovoda od čvora Međimurje do CPS-a Molve

Tijekom proljeća 2016. godine izvršen je terenski pregled trase otpremnog plinovod od čvora Međimurje do centralne plinske stanice (CPS) Molve DN 300/75 na području grada Koprivnice, općina Legrad, Rasinja, Koprivnički Ivanec, Koprivnički Bregi, Hlebine, Novigrad Podravski i Virje. Tijekom terenskog pregleda zabilježeno je 29 arheoloških lokaliteta koji se datiraju u razdoblja pretpovijesti, antike i srednjeg vijeka. U ovom se radu prezentiraju rezultati preliminarne analize pronađenog materijala i daje se okvirna datacija lokaliteta