PROCEEDINGS OF THE LATVIAN ACADEMY OF SCIENCES

SECTION B: NATURAL, EXACT AND APPLIED SCIENCES
(ISSN 1407-009X, Language: English)

Volume 58 (2004) Number 1

INTRACELLULAR TRAFFICKING AND FUNCTIONAL ACTIVITY OF NUCLEAR FACTORS OF ACTIVATED T CELLS ARE DIFFERENTLY AFFECTED BY CYCLOSPORIN A

Inna Iņaškina, Edgar Serfling^*, and Ēriks Jankevics
Biomedical Research and Study Centre, University of Latvia, Rātsupītes ielā 1, Rīga LV-1067, Latvia; E-mail: inna@biomed.lu.lv
^*Department of Molecular Pathology, Institute of Pathology, University of Wuerzburg, Wuerzburg, Germany
Proc. Latvian Acad. Sci., Section B, Vol. 58 (2004), No. 1, pp. 1–8

The intracellular translocation of members of the nuclear factor of activated T cells (NFAT) transcription factors family is mediated by the activity of Ca²⁺-dependent serine/threonine phosphotase calcineurin that can be specifically inhibited by cyclosporin A (CsA). We investigated the localisation and conditions of nuclear translocation of NFATc1, NFATc2, and NFATc3 in various T- and B-cell lines. Our results suggest distinct behaviour of NFAT factors in response to treatment with CsA. Whereas the nuclear residence of NFATc2 and NFATc3 is always sensitive to treatment with CsA, i.e., these proteins are exported back to the cytoplasm, NFATc1 is considerably less affected by CsA and does not leave the cell nucleus. NFATc1 in high concentration forms granular structures within the cell nuclei. The treatment of cells with CsA leads to a decrease in the mobility of NFAT proteins during electrophoresis due to hyperphosphorylation. These observations are validated by western blots, immunostaining, and confocal microscopy of chimeric NFAT, green fluorescent protein. In addition, functional studies show that CsA inhibits transcription activity of endogenous NFATc1, but it has no effect on the overexpressed protein.

Key words: nuclear factor of activated T-cells, cytoplasmic/nuclear shuttling, cyclosporin A, protein phosphorylation.

STUDIES ON THE INTERACTION BETWEEN THE OPIOID AND MELANOCORTIN-ERGIC SYSTEMS: DYNORPHIN BINDING MELANOCORTIN RECEPTORS

Baiba Štāmere, Līga Krīgere, Kristīne Saleniece, Uldis Vikmanis, and Ruta Muceniece
Faculty of Medicine, University of Latvia, Šarlotes ielā 1a, Rīga LV-1001, LATVIA
E-mail: rutam@latnet.lv
Proc. Latvian Acad. Sci., Section B, Vol. 58 (2004), No. 1, pp. 9–13

Non-opioid binding sites for dynorphins have been demonstrated in a number of tissues, but the identity of these sites up to now have not been determined. Dynorphins antagonise melanocortin-(MC) stimulated cAMP generation in vitro with potencies similar for pharmacological non-opioid effects of dynorphins in vivo. Therefore, we have suggested that dynorphins may act via melanocortin receptors (MCRs). We tested this hypothesis by radioligand binding approaches. However, we found very low binding affinities of dynorphin A(1–17), dynorphin A (2–17), dynorphin A(2–11), dynorphin A(1–13), and non-binding of the dynorphin B, a-neo-endorphin, enkephalins, and dynorphin A (1–6) to all subtypes of MCRs. This contradicts the earlier report of a high dynorphin potency to antagonise cAMP generation stimulated by MCs.

Key words: dynorphins, melanocortins, radioligand binding, melanocortin receptors.

A MATHEMATICAL MODEL FOR THE DAUGAVA RIVER ICE PROCESSES

Guntis Zaķis, Ansis Zīverts, and Inese Huttunen^*
Latvia University of Agriculture, Akadēmijas ielā 19, Jelgava LV-3001, LATVIA
^*Finnish Environment Institute, Mechelininkatu 34a P.O.BOX 140, 00251 Helsinki, FINLAND
E-mail: nara@latnet.lv; ziverts@latnet.lv; Inese.huttunen@Ymparisto.fi
Proc. Latvian Acad. Sci., Section B, Vol. 58 (2004), No. 1, pp. 14–23

A mathematical model was developed to analyse ice phenomena and hydraulic conditions in a length of 250 km in the Daugava River, from the border of Latvia to the Pļaviņas hydropower plant. In the model, ice formation and deterioration processes were designed similarly to already known mathematical models of ice processes for one-dimensional river flows. The Mathematical Model for the Daugava River Ice Processes was developed for a branched riverbed system with loops. To analyse the river flow, the Daugava below the town of Jēkabpils was conditionally divided into three study branches. The model output data were compared to field observations data of water level and ice volume.

Key words: river ice processes, mathematical modelling, skim and frazil ice, unsteady flow hydraulics

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