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排序方式: 共有492条查询结果,搜索用时 15 毫秒
71.
Boris Malyarchuk Miroslava Derenko Tomasz Grzybowski Maria Perkova Urszula Rogalla Tomas Vanecek Iosif Tsybovsky 《PloS one》2010,5(4)
It is generally accepted that the most ancient European mitochondrial haplogroup, U5, has evolved essentially in Europe. To resolve the phylogeny of this haplogroup, we completely sequenced 113 mitochondrial genomes (79 U5a and 34 U5b) of central and eastern Europeans (Czechs, Slovaks, Poles, Russians and Belorussians), and reconstructed a detailed phylogenetic tree, that incorporates previously published data. Molecular dating suggests that the coalescence time estimate for the U5 is ∼25–30 thousand years (ky), and ∼16–20 and ∼20–24 ky for its subhaplogroups U5a and U5b, respectively. Phylogeographic analysis reveals that expansions of U5 subclusters started earlier in central and southern Europe, than in eastern Europe. In addition, during the Last Glacial Maximum central Europe (probably, the Carpathian Basin) apparently represented the area of intermingling between human flows from refugial zones in the Balkans, the Mediterranean coastline and the Pyrenees. Age estimations amounting for many U5 subclusters in eastern Europeans to ∼15 ky ago and less are consistent with the view that during the Ice Age eastern Europe was an inhospitable place for modern humans. 相似文献
72.
Urszula Zajączkowska 《Planta》2014,240(6):1203-1211
Main conclusion
Stump overgrowth may serve as a unique model for studying cellular reorganization and mechanisms responsible for cell polarity changes during the process of vascular tissue differentiation from initially unorganized parenchymatous cells. Cellular ordering and tissue reorganization during the overgrowth process of the transverse surfaces of Douglas fir stumps in forest stand was studied. At the beginning of stump overgrowth, the produced parenchymatous cells form an unorganized tissue. Particular parenchyma cells start arranging into more ordered structures which resemble rays. Application of digital image analysis software based on structure tensor was used. The analysis showed that at this stage of tissue development, cellular elements display a wide range of angular orientation values and attain very low coherency coefficients. The progress of the tissue differentiation process is associated with the formation of local regions with tracheids oriented circularly around the rays. This coincides with an increase in the range of angular orientations and greater values of coherency coefficients. At the most advanced stage of tissue development, with tracheids arranged parallelly in longitudinal strands, the degree of cell ordering is the highest what is manifested by the greatest values attained by coherency coefficients, and the narrow range of angular orientations. It is suggested that the ray-like structures could act as organizing centers in the morphogenetic field responsible for differentiation of the overgrowth tissue. The circular pattern of tracheids around rays in the initial phase of tissue development can be interpreted in terms of local rotation of the morphogenetic field which afterward is transformed into irrotational field. This transformation is noted by the presence of tracheids arranged parallelly in longitudinal strands. The possible involvement of a mechanism controlling cell polarity with respect to auxin transport is discussed. 相似文献73.
Kuban-Jankowska A Knap N Gorska M Popowska U Wozniak M 《Biochemical and biophysical research communications》2011,415(2):270-273
We have designed a useful method of assessing reactive oxygen species generation in biological fluids. The novel assay utilizes tyrosine phosphatase CD45 as a biosensor of oxidative stress. Applying this new method, we examined oxygen species generation in the following cell culture media: RPMI 1640, DMEM, DMEM enriched with pyruvate and MEM. We discovered that the media (especially RPMI 1640) significantly reduced the activity of protein tyrosine phosphatase. The media-caused inactivation of CD45 was reversible after treatment with dithiothreitol being a powerful reducing agent. Interestingly, the media supplemented with catalase did not exhibit any inhibitory effect on CD45 activity which suggests a hydrogen peroxide-mediated mechanism of the enzyme inactivation. In addition to that, we assessed the impact of oxidative stress level on the activity of CD45 as measured in Jurkat cells cultured in RPMI 1640 either exposed or not exposed to the light of laminar flow cabinet fluorescent lamp. We found that Jurkat cells that were exposed to light displayed ca. 20% lower activity of CD45 than the cells protected against the light. The obtained results indicate that production of hydrogen peroxide in the medium leading to inhibition of CD45 was light-dependent, and that careful protection of cell culture media from the light may help to prevent the artifact in cell studies. Hydrogen peroxide, responsible for CD45 inactivation, can be generated in cell culture media after exposition to light due to photoreactive amino acids present in the media. 相似文献
74.
Piotrowska U Adler G Kozicki I 《Biochemical and biophysical research communications》2011,414(2):350-354
The functioning of heterotrimeric G protein α subunits in the transduction of hormonal signals to appropriate intracellular responses is well recognized. Much less is known about the distribution of isoforms and functions of G protein β subunits. Here, using specific antibodies, we documented that in plasma membranes of the thyroid cell line Nthy-ori 3-1 all Gβ isoforms-Gβ1, Gβ2, Gβ3, Gβ4 and Gβ5 are present, while the Gβ3 occurs in minute amount. In plasma membrane fraction isolated from pooled postoperative thyroids of patients with nodular goiter and Graves’ disease, the Gβ1, Gβ2, Gβ4 and Gβ5 subunits were found, whereas Gβ3 could not be detected.Competition studies revealed that the Gβ2 is the principal Gβ subunit in membranes from cultured thyroid cells, originated from normal thyroid, as well as in membranes from patients’ thyroids. This suggests that Gβ2 subunit cooperates with Gαs subunit, the most active of the Gα variants, during stimulation of adenylate cyclase which constitutes the main route of physiological thyroid stimulation. 相似文献
75.
Cardiomyocytes have a complex Ca2+ behavior and changes in this behavior may underlie certain disease states. Intracellular Ca2+ activity can be regulated by the phospholipase Cβ–Gαq pathway localized on the plasma membrane. The plasma membranes of cardiomycoytes are rich in caveolae domains organized by caveolin proteins. Caveolae may indirectly affect cell signals by entrapping and localizing specific proteins. Recently, we found that caveolin may specifically interact with activated Gαq, which could affect Ca2+ signals. Here, using fluorescence imaging and correlation techniques we show that Gαq-Gβγ subunits localize to caveolae in adult ventricular canine cardiomyoctyes. Carbachol stimulation releases Gβγ subunits from caveolae with a concurrent stabilization of activated Gαq by caveolin-3 (Cav3). These cells show oscillating Ca2+ waves that are not seen in neonatal cells that do not contain Cav3. Microinjection of a peptide that disrupts Cav3-Gαq association, but not a control peptide, extinguishes the waves. Furthermore, these waves are unchanged with rynaodine treatment, but not seen with treatment of a phospholipase C inhibitor, implying that Cav3-Gαq is responsible for this Ca2+ activity. Taken together, these studies show that caveolae play a direct and active role in regulating basal Ca2+ activity in cardiomyocytes. 相似文献
76.
In many biochemical reactions occurring in living cells, number of various molecules might be low which results in significant stochastic fluctuations. In addition, most reactions are not instantaneous, there exist natural time delays in the evolution of cell states. It is a challenge to develop a systematic and rigorous treatment of stochastic dynamics with time delays and to investigate combined effects of stochasticity and delays in concrete models.We propose a new methodology to deal with time delays in biological systems and apply it to simple models of gene expression with delayed degradation. We show that time delay of protein degradation does not cause oscillations as it was recently argued. It follows from our rigorous analysis that one should look for different mechanisms responsible for oscillations observed in biological experiments.We develop a systematic analytical treatment of stochastic models of time delays. Specifically we take into account that some reactions, for example degradation, are consuming, that is: once molecules start to degrade they cannot be part in other degradation processes.We introduce an auxiliary stochastic process and calculate analytically the variance and the autocorrelation function of the number of protein molecules in stationary states in basic models of delayed protein degradation. 相似文献
77.
Marzec-Wróblewska U Kamiński P Lakota P Szymański M Wasilow K Ludwikowski G Kuligowska-Prusińska M Odrowąż-Sypniewska G Stuczyński T Michałkiewicz J 《Biological trace element research》2011,143(1):167-177
The aim of the present study was to measure zinc (Zn) and iron (Fe) concentration in human semen and superoxide dismutase
(SOD) activity in seminal plasma and correlate the results with sperm quality. Semen samples were obtained from men (N = 168) undergoing routine infertility evaluation. The study design included two groups based on the ejaculate parameters.
Group I (n = 39) consisted of males with normal ejaculate (normozoospermia), and group II (n = 129) consisted of males with pathological spermiogram. Seminal Zn and Fe were measured in 162 samples (group I, n = 38; group II, n = 124) and SOD activity in 149 samples (group I, n = 37; group II, n = 112). Correlations were found between SOD activity and Fe and Zn concentration, and between Fe and Zn concentration. SOD
activity was negatively associated with volume of semen and positively associated with rapid progressive motility, nonprogressive
motility, and concentration. Negative correlation was stated between Fe concentration and normal morphology. Mean SOD activity
in seminal plasma of semen from men of group I was higher than in seminal plasma of semen from men of group II. Fe concentration
was higher in teratozoospermic males than in males with normal morphology of spermatozoa in group II. Our results suggest
that Fe may influence spermatozoa morphology. 相似文献
78.
Ambroziak U Pachucki J Bednarczuk T Pogorzelski R Toutounchi S Bogdańska M Koperski L Bar-Andziak E 《Endokrynologia Polska》2011,62(5):466-470
Bacterial thyroiditis is a rare disease, and one of which the clinical symptoms and signs are frequently misleading. On the other hand, prompt diagnosis is crucial for successful treatment. We report the case of an 82 year-old man with diabetes mellitus type 2 and a history of steroid treatment who presented with severe odynophagia and dysphagia associated with fever, chills, sore throat and right ear pain. Based on the clinical picture, radiological studies, thyroid cytology, blood and thyroid aspirate culture, suppurative thyroiditis caused by Salmonella enteritidis was diagnosed. The patient was successfully treated with antibiotics and surgical drainage. 相似文献
79.
Kang BS Cooper DR Devedjiev Y Derewenda U Derewenda ZS 《Structure (London, England : 1993)》2003,11(7):845-853
Crystal structures of the PDZ2 domain of the scaffolding protein syntenin, both unbound and in complexes with peptides derived from C termini of IL5 receptor (alpha chain) and syndecan, reveal the molecular roots of syntenin's degenerate specificity. Three distinct binding sites (S(0), S(-1), and S(-2)), with affinities for hydrophobic side chains, function in a combinatorial way: S(-1) and S(-2) act together to bind syndecan, while S(0) and S(-1) are involved in the binding of IL5Ralpha. Neither mode of interaction is consistent with the prior classification scheme, which defined the IL5Ralpha interaction as class I (-S/T-X-phi) and the syndecan interaction as class II (-phi-X-phi). These results, in conjunction with other emerging structural data on PDZ domains, call for a revision of their classification and of the existing model of their mechanism. 相似文献
80.