Cirkadiánní regulace fyziologických funkcí ve zdraví a nemoci

Přírodovědecká fakult

Modulation of NMDA-Mediated Clock Resetting in the Suprachiasmatic Nuclei of mPer2Luc Mouse by Endocannabinoids

Light entrains the master circadian clock in the suprachiasmatic nucleus (SCN) predominantly through glutamatergic signaling via NMDA receptors. The magnitude and the direction of resulting phase shifts depend on timing of the photic stimulus. Previous reports based on behavioral and electrophysiological data suggested that endocannabinoids (EC) might reduce the ability of the SCN clock to respond to light. However, there is little direct evidence for the involvement of EC in entrainment of the rhythmic clock gene expression in the SCN. We have used luminescence recording of cultured SCN slices from mPer2Luc mice to construct a complete phase response curve (PRC) for NMDA receptor activation. The results demonstrated that NMDA administration phase-shifts the PER2 rhythm in a time-specific manner. A stable “singularity,” in the course of which the clock seemingly stops while the overall phase is caught between delays and advances, can occur in response to NMDA at a narrow interval during the PER2 level decrease. NMDA-induced phase delays were affected neither by the agonist (WIN 55,212-2 mesylate) nor by the antagonist (rimonabant hydrochloride) of EC receptors. However, the agonist significantly reduced the NMDA-induced phase advance of the clock, while the antagonist enhanced the phase advance, causing a shift in the sensitivity window of the SCN to NMDA. The modulation of EC signaling in the SCN had no effect by itself on the phase of the PER2 rhythm. The results provide evidence for a modulatory role of EC in photic entrainment of the circadian clock in the SCN

Setting the biological time in central and peripheral clocks during ontogenesis

AbstractIn mammals, the principal circadian clock within the suprachiasmatic nucleus (SCN) entrains the phase of clocks in numerous peripheral tissues and controls the rhythmicity in various body functions. During ontogenesis, the molecular mechanism responsible for generating circadian rhythmicity develops gradually from the prenatal to the postnatal period. In the beginning, the maternal signals set the phase of the newly developing fetal and early postnatal clocks, whereas the external light–dark cycle starts to entrain the clocks only later. This minireview discusses the complexity of signaling pathways from mothers and the outside world to the fetal and newborn animals’ circadian clocks

Targeted modification of the Per2 clock gene alters circadian function in mPer2luciferase (mPer2Luc) mice.

Modification of the Per2 clock gene in mPer2Luc reporter mice significantly alters circadian function. Behavioral period in constant dark is lengthened, and dissociates into two distinct components in constant light. Rhythms exhibit increased bimodality, enhanced phase resetting to light pulses, and altered entrainment to scheduled feeding. Mechanistic mathematical modelling predicts that enhanced protein interactions with the modified mPER2 C-terminus, combined with differential clock regulation among SCN subregions, can account for effects on circadian behavior via increased Per2 transcript and protein stability. PER2::LUC produces greater suppression of CLOCK:BMAL1 E-box activity than PER2. mPer2Luc carries a 72 bp deletion in exon 23 of Per2, and retains a neomycin resistance cassette that affects rhythm amplitude but not period. The results show that mPer2Luc acts as a circadian clock mutation illustrating a need for detailed assessment of potential impacts of c-terminal tags in genetically modified animal models

Conserved Expression of the Glutamate NMDA Receptor 1 Subunit Splice Variants during the Development of the Siberian Hamster Suprachiasmatic Nucleus

Glutamate neurotransmission and the N-methyl-D-aspartate receptor (NMDAR) are central to photic signaling to the master circadian pacemaker located in the hypothalamic suprachiasmatic nucleus (SCN). NMDARs also play important roles in brain development including visual input circuits. The functional NMDAR is comprised of multiple subunits, but each requiring the NR1 subunit for normal activity. The NR1 can be alternatively spliced to produce isoforms that confer different functional properties on the NMDAR. The SCN undergoes extensive developmental changes during postnatal life, including synaptogenesis and acquisition of photic signaling. These changes are especially important in the highly photoperiodic Siberian hamster, in which development of sensitivity to photic cues within the SCN could impact early physiological programming. In this study we examined the expression of NR1 isoforms in the hamster at different developmental ages. Gene expression in the forebrain was quantified by in situ hybridization using oligonucleotide probes specific to alternatively spliced regions of the NR1 heteronuclear mRNA, including examination of anterior hypothalamus, piriform cortex, caudate-putamen, thalamus and hippocampus. Gene expression analysis within the SCN revealed the absence of the N1 cassette, the presence of the C2 cassette alone and the combined absence of C1 and C2 cassettes, indicating that the dominant splice variants are NR1-2a and NR1-4a. Whilst we observe changes at different developmental ages in levels of NR1 isoform probe hybridization in various forebrain structures, we find no significant changes within the SCN. This suggests that a switch in NR1 isoform does not underlie or is not produced by developmental changes within the hamster SCN. Consistency of the NR1 isoforms would ensure that the response of the SCN cells to photic signals remains stable throughout life, an important aspect of the function of the SCN as a responder to environmental changes in quality/quantity of light over the circadian day and annual cycle

Glycosylation and antigenic properties of Phlebotomus perniciosus and P. orientalis salivary proteins

Cílem této práce bylo zmapovat glykosylaci a antigenní vlastnosti slinných proteinů dvou druhů flebotomů, Phlebotomus perniciosus a P. orientalis, kteří jsou významnými vektory viscerální leishmaniózy. Pomocí afinoblotu se značenými lektiny jsme prokázali, že řada slinných proteinů obou studovaných druhů flebotomů je N-glykosylována, přítomnost O-glykosylací nebylo možné potvrdit. Úroveň N-glykosylace většiny těchto proteinů je poměrně nízká, větší množství potenciálních N-glykosylačních míst bylo nalezeno pouze v aminokyselinových sekvencích hyaluronidázy P. orientalis a endonukleáz obou testovaných druhů. Pro expresi v bakteriálním expresním systému byly vybrány čtyři slinné antigenní proteiny P. perniciosus, z nichž dva proteiny (PpeSP01 a PpeSP01B) nebyly glykosylovány a úroveň glykosylace zbylých dvou proteinů (PpeSP03B a PpeSP07) byla nízká. Antigenní vlastnosti čtyř vybraných rekombinantních proteinů P. perniciosus byly následně testovány prostřednictvím imunoblotu a ELISA testů. Během počátečních pokusů se séry experimentálně exponovaných psů se dva proteiny (rSP07 a rSP01B) ukázaly jako nevhodné a byly tudíž z dalších experimentů vyřazeny. Rekombinantní proteiny rSP03B a rSP01 byly rozeznávány stejnými IgG protilátkami jako nativní formy těchto proteinů ze slinných žláz P. perniciosus....The goal of this study was to map the glycosylation pattern and antigenic properties of the salivary proteins of two closely related sand fly species, Phlebotomus perniciosus and P. orientalis. Affinity blotting with commercially available lectins revealed that many salivary proteins of these species are N-glycosylated, while the presence of O-glycosylation could not be confirmed. The level of N-glycosylation of most of these proteins is quite low, a larger number of potential N-glycosylation sites were found only in the amino acid sequences of P. orientalis hyaluronidase and endonucleases of both species tested. Four antigens from P. perniciosus salivary glands were selected for expression in a bacterial expression system; two of these proteins (PpeSP01 and PpeSP01B) were not glycosylated and the glycosylation level of the remaining two (PpeSP03B and PpeSP07) was low. The antigenic properties of the four chosen recombinant proteins were subsequently tested using immunoblot and ELISA. During the initial experiments with the sera of dogs experimentally bitten by P. perniciosus, two proteins (rSP07 and rSP01B) were proven unsuitable and they were excluded from further experiments. Recombinant proteins rSP03B and rSP01 were recognized by the same IgG antibodies as the native forms of these proteins...Department of ParasitologyKatedra parazitologiePřírodovědecká fakultaFaculty of Scienc

Job satisfaction analysis in the company TOMOS, a.s.

The presented diploma thesis is a practical research of job satisfaction in the chosen company Tomos Praha, a.s. It deals with the theoretical background of job satisfaction, its relation to the motivation and its impact on the performance of the employees. It describes particular theories of job satisfaction and focuses on the factors which influence the job satisfaction. In the practical part it examines the job satisfaction in the company Tomos Praha, a.s. from the different point of view, analyses the the data acquired by the empirical research and proposes the steps for improving the current situation

Salivary glycoproteins of bloodsucking arthropods

During obtaining their blood meal, bloodsucking arthropods salivate into their host. Bloodsucking arthropods' saliva contains wide array of bioactive macromolecules. Host organism develops antibody response against many of these molecules. Due to interspecies variability in salivary protein composition, detection of antibody response may serve as a marker of the exposure to individual species of bloodsucking arthropods. Host antibody response is mostly elicited by proteins or glycoproteins. Glycoproteins contain one or more oligosaccharide chains attached to the protein. Glycoprotein's antigenicity could be caused by either both parts, or by only the protein, or the sugar part. This fact has to be taken into consideration for choice of the expression system for recombinant glycoprotein synthesis. This work summarizes current knowledge about structure, function and features of salivary glycoproteins in various species of bloodsucking arthropods

Toky a centra obchodu s diamanty ve světové ekonomice

Bakalářská práce se zabývá velmi vzácnou a hodnotnou komoditou - diamanty. Zaměřuje se na obecnou charakteristiku diamantů, jejich vlastnosti, historii či vznik, ale především analyzuje producentské oblasti a mezinárodní obchod s diamanty. V poslední části pojednává o smutném fenoménu 90. let minulého století - tzv. konfliktních diamantech, kterými byly financovány kruté občanské války v některých afrických státech