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161.
Mari Pekkanen-Mattila Markku Pelto-Huikko Ville Kujala Riitta Suuronen Heli Skottman Katriina Aalto-Setälä Erja Kerkelä 《Histochemistry and cell biology》2010,133(5):595-606
Human embryonic stem cell (hESC) differentiation in embryoid bodies (EBs) provides a valuable tool to study the interplay
of different germ layers and their influence on cell differentiation. The gene expression of the developing EBs has been shown
in many studies, but the protein expression and the spatial composition of different germ layers in human EBs have not been
systematically studied. The aim of the present work was to study the temporal and spatial organisation of germ layers based
on the expression of mesoderm (Brachyury T), endoderm (AFP) and ectoderm (SOX1) markers during the early stages of differentiation
in eight hESC lines. Tissue multi-array technology was applied to study the protein expression of a large number of EBs. According
to our results, EB formation and the organisation of germ layers occurred in a similar manner in all the lines. During 12 days
of differentiation, all the germ layer markers were present, but no obvious distinct trajectories were formed. However, older
EBs were highly organised in structure. Pluripotency marker OCT3/4 expression persisted unexpectedly long in the differentiating
EBs. Cavity formation was observed in the immunocytological sections, and caspase-3 expression was high, suggesting a role
of apoptosis in hESC differentiation and/or EB formation. The expression of Brachyury T was notably low in all the lines,
also those with the best cardiac differentiation capacity, while the expression of SOX1 was higher in some lines, suggesting
that the neural differentiation propensity may be detectable already in the early stages of EB differentiation. 相似文献
162.
Helena Gylling Maarit Hallikainen Jussi Pihlajam?ki Piia Simonen Johanna Kuusisto Markku Laakso Tatu A. Miettinen 《Journal of lipid research》2010,51(8):2422-2427
Cholesterol synthesis is upregulated and absorption downregulated in insulin resistance and in type 2 dia-betes. We investigated whether alterations in cholesterol metabolism are observed across the glucose tolerance status, from normoglycemia through impaired glucose tolerance to type 2 diabetes, in 781 randomly selected men 45 to 70 years of age from a population-based Metabolic Syndrome in Men Study. Cholesterol metabolism was assayed using surrogate serum markers, squalene, and noncholesterol sterols. The study population was classified into subgroups according to glucose tolerance as follows: normoglycemia, impaired fasting glucose, impaired glucose tolerance, and type 2 diabetes. LDL cholesterol did not differ between the groups. Cholesterol synthesis markers were lowest and absorption markers highest in normoglycemia. Sitosterol was lower in subjects with impaired fasting glucose compared with normoglycemic subjects (113 ± 7 vs. 136 ± 3 102 μmol/mmol of cholesterol, P < 0.05). LDL cholesterol was not associated with lathosterol/sitosterol ratio, a marker of cholesterol metabolism. Peripheral insulin sensitivity evaluated by the Matsuda index was associated with the lathosterol/sitosterol ratio in the entire population (r = −0.457, P < 0.001) and with that of lathosterol/cholestanol independently of obesity. In conclusion, cholesterol metabolism was altered already from subjects with impaired fasting glucose. Upregulated cholesterol synthesis was associated with peripheral insulin resistance independent of obesity. 相似文献
163.
Markku Larjavaara 《Journal of theoretical biology》2010,265(1):63-124
Wind routinely topples trees during storms, and the likelihood that a tree is toppled depends critically on its allometry. Yet none of the existing theories to explain tree allometry consider wind drag on tree canopies. Since leaf area index in crowded, self-thinning stands is independent of stand density, the drag force per unit land can also be assumed to be independent of stand density, with only canopy height influencing the total toppling moment. Tree stem dimensions and the self-thinning biomass can then be computed by further assuming that the risk of toppling over and stem maintenance per unit land area are independent of stand density, and that stem maintenance cost is a linear function of stem surface area and sapwood volume. These assumptions provide a novel way to understand tree allometry and lead to a self-thinning line relating tree biomass and stand density with a power between −3/2 and −2/3 depending on the ratio of maintenance of sapwood and stem surface. 相似文献
164.
Marshall Nathaniel S. Grunstein Ron R. Peltonen Markku Stenlof Kaj Hedner Jan Sjostrom Lars V. 《Sleep and biological rhythms》2010,8(1):63-71
Sleep and Biological Rhythms - Sleep duration has been linked to obesity and/or weight gain in a number of cross-sectional and longitudinal observational studies. The Swedish Obese Subjects Study... 相似文献
165.
Anne Kultti Riikka K?rn? Kirsi Rilla Pertti Nurminen Elina Koli Katri M. Makkonen Jutong Si Markku I. Tammi Raija H. Tammi 《The Journal of biological chemistry》2010,285(30):22901-22910
Hyaluronan synthases (HAS1–3) are integral plasma membrane proteins that synthesize hyaluronan, a cell surface and extracellular matrix polysaccharide necessary for many biological processes. It has been shown that HAS is partly localized in cholesterol-rich lipid rafts of MCF-7 cells, and cholesterol depletion with methyl-β-cyclodextrin (MβCD) suppresses hyaluronan secretion in smooth muscle cells. However, the mechanism by which cholesterol depletion inhibits hyaluronan production has remained unknown. We found that cholesterol depletion from MCF-7 cells by MβCD inhibits synthesis but does not decrease the molecular mass of hyaluronan, suggesting no major influence on HAS stability in the membrane. The inhibition of hyaluronan synthesis was not due to the availability of HAS substrates UDP-GlcUA and UDP-GlcNAc. Instead, MβCD specifically down-regulated the expression of HAS2 but not HAS1 or HAS3. Screening of signaling proteins after MβCD treatment revealed that phosphorylation of Akt and its downstream target p70S6 kinase, both members of phosphoinositide 3-kinase-Akt pathway, were inhibited. Inhibitors of this pathway suppressed hyaluronan synthesis and HAS2 expression in MCF-7 cells, suggesting that the reduced hyaluronan synthesis by MβCD is due to down-regulation of HAS2, mediated by the phosphoinositide 3-kinase-Akt-mTOR-p70S6K pathway. 相似文献
166.
Rytkönen AK Vaara M Nethanel T Kaufmann G Sormunen R Läärä E Nasheuer HP Rahmeh A Lee MY Syväoja JE Pospiech H 《The FEBS journal》2006,273(13):2984-3001
The contributions of human DNA polymerases (pols) alpha, delta and epsilon during S-phase progression were studied in order to elaborate how these enzymes co-ordinate their functions during nuclear DNA replication. Pol delta was three to four times more intensely UV cross-linked to nascent DNA in late compared with early S phase, whereas the cross-linking of pols alpha and epsilon remained nearly constant throughout the S phase. Consistently, the chromatin-bound fraction of pol delta, unlike pols alpha and epsilon, increased in the late S phase. Moreover, pol delta neutralizing antibodies inhibited replicative DNA synthesis most efficiently in late S-phase nuclei, whereas antibodies against pol epsilon were most potent in early S phase. Ultrastructural localization of the pols by immuno-electron microscopy revealed pol epsilon to localize predominantly to ring-shaped clusters at electron-dense regions of the nucleus, whereas pol delta was mainly dispersed on fibrous structures. Pol alpha and proliferating cell nuclear antigen displayed partial colocalization with pol delta and epsilon, despite the very limited colocalization of the latter two pols. These data are consistent with models where pols delta and epsilon pursue their functions at least partly independently during DNA replication. 相似文献
167.
Heini Kallio Silvia Pastorekova Jaromir Pastorek Abdul Waheed William S Sly Susanna Mannisto Markku Heikinheimo Seppo Parkkila 《BMC developmental biology》2006,6(1):22
Background
Of the thirteen active carbonic anhydrase (CA) isozymes, CA IX and XII have been linked to carcinogenesis. It has been suggested that these membrane-bound CAs participate in cancer cell invasion, which is facilitated by an acidic tumor cell environment. Since active cell migration is a characteristic feature of embryonic development, we set out to explore whether these isozymes are expressed in mouse embryos of different ages. The studies were focused on organogenesis stage. 相似文献168.
Raulio M Pore V Areva S Ritala M Leskelä M Lindén M Rosenholm JB Lounatmaa K Salkinoja-Salonen M 《Journal of industrial microbiology & biotechnology》2006,33(4):261-268
The aim of the present work was to explore possibilities of photocatalytic TiO2 coating for reducing biofilms on non-living surfaces. The model organism, Deinococcus geothermalis, known to initiate growth of durable, colored biofilms on machine surfaces in the paper industry, was allowed to form biofilms
on stainless steel, glass and TiO2 film coated glass or titanium. Field emission electron microscopy revealed that the cells in the biofilm formed at 45°C under
vigorous shaking were connected to the surface by means of numerous adhesion threads of 0.1--0.3 μm in length. Adjacent cells
were connected to one another by threads of 0.5--1 μm in length. An ultrastructural analysis gave no indication for the involvement
of amorphous extracellular materials (e.g., slime) in the biofilm. When biofilms on photocatalytic TiO2 surfaces, submerged in water, were exposed to 20 W h m−2 of 360 nm light, both kinds of adhesion threads were completely destroyed and the D. geothermalis cells were extensively removed (from >107 down to below 106 cells cm−2). TiO2 films prepared by the sol-gel technique were slightly more effective than those prepared by the ALD technique. Doping of
the TiO2 with sulfur did not enhance its biofilm-destroying capacity. The results show that photocatalytic TiO2 surfaces have potential as a self-cleaning technology for warm water using industries. 相似文献
169.
Järvinen P Palmé A Orlando Morales L Lännenpää M Keinänen M Sopanen T Lascoux M 《American journal of botany》2004,91(11):1834-1845
The phylogenetic relationships within the genus Betula (Betulaceae) were investigated using a part of the nuclear ADH gene and DNA sequences of the chloroplast matK gene with parts of its flanking regions. Two well-supported phylogenetic groups could be identified in the chloroplast DNA sequence: one containing the three American species B. lenta, B. alleghaniensis, and B. papyrifera and the other including all the other species studied. The ADH gene displayed more variation, and three main groups could be identified. In disagreement with the classical division of the genus Betula, B. schmidtii and B. nana grouped with the species in subgenus Betula, and B. ermanii grouped with species in subgenus Chamaebetula, including B. humilis and B. fruticosa. The ADH phylogeny suggests that several independent polyploidizations within the genus Betula could have taken place. The ADH and chloroplast phylogenies were in part incongruent due to the placement of B. papyrifera. The most likely reason for this seems to be cytoplasmic introgression. 相似文献
170.
We studied the body mass variation from autumn to winter, in a free-living population of willow tits (Parus montanus), a food-hoarding passerine living year-round in boreal forests. Our aim was to find out whether this population exhibits winter fattening as part of the annual body mass cycle. True winter fattening is considered to be a strategic response to winter conditions. The strategy includes an increase in both the morning mass and the daily mass increase, as winter approaches. A multivariate approach was used to find which predictors (year, date, age, sex, body size, temperature and snow depth) explained the mass variation in birds measured twice per day. Morning mass variation was explained by sex, age, wing length and snow depth. Independently, date explained morning mass variation only in adult males. None of the predictors explained the variation observed in daily mass increase in any age or sex class. Therefore, we failed to detect winter fattening in our study population of willow tits. Response to increasing night length is not due to higher absolute intake, but to higher energy acquisition rate and decreased night-time energy consumption. The results suggest that willow tits at high latitudes manage increasing energy demands on a short-term basis and respond flexibly to changing conditions by adjusting foraging efficiency and especially night-time energy expenditure. 相似文献