Inter-clutch egg size variation in kestrels Falco tinnunculus: seasonal decline under fluctuating food conditions

We examined inter-clutch egg size variation of Eurasian kestrels Falco tinnunculus in western Finland over a period of 12 years, during which their main prey, Microtus voles, fluctuated in three-year population cycles. Females that bred twice in the area had highly repeatable egg size, and the main part of the observed variation was likely to be due to among-female differences. Laying date also explained some variation in egg size, but compared to the variation between individuals its effect was small and varied among the phases of the vole cycle. During decrease phases and years with low vole abundance mean egg size of clutches declined with laying date, whereas during increase phases mean egg size remained stable within the season. Although egg size was not related to fledging success, we found that egg size may have value for the development of eggs as the probability of total hatching success of a clutch increased with increasing mean egg size.     

Determination of Mercury and Methylmercury in Hair of the Czech Children’s Population

The developed method for mercury speciation analysis has been validated and used for the biomonitoring study of mercury species in human hair. Statistical evaluation proved the reliability of simplified determination of inorganic mercury (difference between total mercury and methylmercury). The results of the validation showed that the method is very well suitable for the determination of both species of mercury in hair for biomonitoring purposes. Non-exposed schoolchildren from three areas in the western and central part of the Czech Republic were chosen as the target group. Tenth of a microgram per gram of the total mercury were generally found in the analyzed hair; values higher than 1 μg g⁻¹ were detected only exceptionally. Comparable results were obtained for two western areas and differed significantly from those for the third area located in the central part of the Czech Republic. In the areas examined, the mean methylmercury contents amounted to 23–46% of the total mercury in the hair. The results confirm an assumption that exposure to mercury does not pose a significant risk to the population in the Czech Republic.     

Calcium-induced contraction of sarcomeres changes the regulation of mitochondrial respiration in permeabilized cardiac cells

The relationships between cardiac cell structure and the regulation of mitochondrial respiration were studied by applying fluorescent confocal microscopy and analysing the kinetics of mitochondrial ADP-stimulated respiration, during calcium-induced contraction in permeabilized cardiomyocytes and myocardial fibers, and in their 'ghost' preparations (after selective myosin extraction). Up to 3 microm free calcium, in the presence of ATP, induced strong contraction of permeabilized cardiomyocytes with intact sarcomeres, accompanied by alterations in mitochondrial arrangement and a significant decrease in the apparent K(m) for exogenous ADP and ATP in the kinetics of mitochondrial respiration. The V(max) of respiration showed a moderate (50%) increase, with an optimum at 0.4 microm free calcium and a decrease at higher calcium concentrations. At high free-calcium concentrations, the direct flux of ADP from ATPases to mitochondria was diminished compared to that at low calcium levels. All of these effects were unrelated either to mitochondrial calcium overload or to mitochondrial permeability transition and were not observed in 'ghost' preparations after the selective extraction of myosin. Our results suggest that the structural changes transmitted from contractile apparatus to mitochondria modify localized restrictions of the diffusion of adenine nucleotides and thus may actively participate in the regulation of mitochondrial function, in addition to the metabolic signalling via the creatine kinase system.     

Formation of highly organized intracellular structure and energy metabolism in cardiac muscle cells during postnatal development of rat heart

Adult cardiomyocytes have highly organized intracellular structure and energy metabolism whose formation during postnatal development is still largely unclear. Our previous results together with the data from the literature suggest that cytoskeletal proteins, particularly βII-tubulin, are involved in the formation of complexes between mitochondria and energy consumption sites. The aim of this study was to examine the arrangement of intracellular architecture parallel to the alterations in regulation of mitochondrial respiration in rat cardiomyocytes during postnatal development, from 1 day to 6 months.     

The role of tubulin in the mitochondrial metabolism and arrangement in muscle cells

Tubulin, a well-known component of the microtubule in the cytoskeleton, has an important role in the transport and positioning of mitochondria in a cell type dependent manner. This review describes different functional interactions of tubulin with cellular protein complexes and its functional interaction with the mitochondrial outer membrane. Tubulin is present in oxidative as well as glycolytic type muscle cells, but the kinetics of the in vivo regulation of mitochondrial respiration in these muscle types is drastically different. The interaction between VDAC and tubulin is probably influenced by such factors as isoformic patterns of VDAC and tubulin, post-translational modifications of tubulin and phosphorylation of VDAC. Important factor of the selective permeability of VDAC is the mitochondrial creatine kinase pathway which is present in oxidative cells, but is inactive or missing in glycolytic muscle and cancer cells. As the tubulin-VDAC interaction reduces the permeability of the channel by adenine nucleotides, energy transfer can then take place effectively only through the mitochondrial creatine kinase/phosphocreatine pathway. Therefore, closure of VDAC by tubulin may be one of the reasons of apoptosis in cells without the creatine kinase pathway. An important question in tubulin regulated interactions is whether other proteins are interacting with tubulin. The functional interaction may be direct, through other proteins like plectins, or influenced by simultaneous interaction of other complexes with VDAC.     

Regional differences among the Finns: a Y-chromosomal perspective

Twenty-two Y-chromosomal markers, consisting of fourteen biallelic markers (YAP/DYS287, M170, M253, P37, M223, 12f2, M9, P43, Tat, 92R7, P36, SRY-1532, M17, P25) and eight STRs (DYS19, DYS385a/b, DYS388, DYS389I/II, DYS390, DYS391, DYS392, DYS393), were analyzed in 536 unrelated Finnish males from eastern and western subpopulations of Finland. The aim of the study was to analyze regional differences in genetic variation within the country, and to analyze the population history of the Finns. Our results gave further support to the existence of a sharp genetic border between eastern and western Finns so far observed exclusively in Y-chromosomal variation. Both biallelic haplogroup and STR haplotype networks showed bifurcated structures, and similar clustering was evident in haplogroup and haplotype frequencies and genetic distances. These results suggest that the western and eastern parts of the country have been subject to partly different population histories, which is also supported by earlier archaeological, historical and genetic data. It seems probable that early migrations from Finno-Ugric sources affected the whole country, whereas subsequent migrations from Scandinavia had an impact mainly on the western parts of the country. The contacts between Finland and neighboring Finno-Ugric, Scandinavian and Baltic regions are evident. However, there is no support for recent migrations from Siberia and Central Europe. Our results emphasize the importance of incorporating Y-chromosomal data to reveal the population substructure which is often left undetected in mitochondrial DNA variation. Early assumptions of the homogeneity of the isolated Finnish population have now proven to be false, which may also have implications for future association studies.     

Suppression of neuronal network excitability and seizure-like events by 2-methyl-4-oxo-3H-quinazoline-3-acetyl piperidine in juvenile rat hippocampus: involvement of a metabotropic glutamate receptor

We present data on the antiepileptic potency of 2-methyl-4-oxo-3H-quinazoline-3-acetyl piperidine (Q5) in juvenile (P9-13) rat hippocampal slices and in particular Q5's action mechanism and target. Q5 (200-500 microM), but not alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA)/Kainate receptor antagonists blocked low-[Mg2+]-induced seizure-like events (SLE) in the CA3 region. Q5 (100 microM) decreased Glu-induced [35S]guanosine 5'-O-(3-thiotriphosphate) binding enhancement in brain homogenates, without interaction with ionotropic Glu receptor sites and Glu transport. In voltage-clamped CA3 pyramidal cells, Q5 (500 microM) depressed activities of spontaneous excitatory and inhibitory postsynaptic currents without affecting miniature inhibitory currents. Metabotropic Glu receptor (mGluR) subtype antagonists affected network excitability dissimilarly. Intracellular Ca2+ ion transients induced by the mGluR agonist (1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD) were suppressed by Q5. Agreeing predictions obtained by modelling Q5 binding to different experimental conformations of mGlu1, Q5 was bound partially to an mGluR binding site in the presence of 1mM ACPD. Findings suggest the apparent involvement of a novel phenotype of action or a new mGluR subtype in the specific suppression of epileptiform activity by Q5 through the depression of network excitability.